Why do chess computers often misevaluate the french defense?

Hello.

Perhaps I am not asking this in the right place (strong players that visit the forums probably know what I mean), but I would like to understand why chess computers often misevaluate the french defence.

For example: 

1.e4 e6 2.d4 d5 3.Nc3 Nf6 4.Bg5 Bb4

Stockfish prefers Black already, but this is one of the mainlines and there have been no signs in theory that Black has an objective advantage here.

There are more examples in this same line (but with 4.e5) as white often has more space, and easier game, sometimes an outpost on d4 (after black plays ...c5 and white takes) etc. It seems like Black is often simply defending passively (or something similar) - perhaps with equality, but no more.

Yet sometimes engines go so far as to claim a slight advantage for Black.

I know it can be quite silly to analyze an opening with an engine, and that I should probably take it's advice as I might take a 1600s advice - with a grain of salt - (except for tactics, as they seem to be quite good at those).

Still, I'd like to understand better why computers often misevaluate the french.

Feel free to post your input.

Never mind, one of my friends answered the question.

Request to mods:
Please lock this forum. 

*edit* 

at the request of Bronsteinpawn please do not lock this forum.

What was his answer?  I'm curious

DONT LOCK IT.

Share your knowledge, I have always been curious of why in the freaking world Stockfish in my phone always says the French Exchange is the best opening lol.

Summarizing my friend's responce and my prior understanding:

• Computers are made by people, and evaluate differently than each other because of this. While the evaluation can be correct or fairly accurate in general, there are exceptions - especially if it is given a set value for a piece/positional advantage that isn't correct in every scenario. 
• Computers can misevaluate dynamic factors - they can see a huge initiative that one side has to find a bunch of only moves to equalize, see the only moves - and equalize - therefore evaluating a position as equal when really it is far easier to play one of the sides.
• A lot of the better endgames for white in the french in which White can press and play for 2 results the engines might evaluate as equal because they (probably) can find the hard moves to defend - as well as horizon effect (which means the winning ideas are beyond its depth)
• Horizon effect - analyzing in the opening means they might miss key lines/ideas, as they are beyond it's depth (there are a lot of already explored ideas in an opening, and it might "prune" some of the good ones out in order to try to increase efficency if it doesn't have access to an opening database). It is often better to use a computer to analyze the middlegame rather than the opening (except for finding tactical resources).
• Closed positions can be harder to plan, the breakthrough of a correct plan can take more than the computers depth if you only let it analyze it breifly. The french 3.Nc3 Nf6 can lead to closed positions after either 4.e5 or 4.Bg5 Bb4 5.e5 - therefore chess engines can miss some important resources.

Personally, I favor the Classical Steinitz Variation 4. e5 where Black effectively loses a tempo with the almost automatic 4...Nfd7 or else posts the N awkwardly.  But even with 4 Bb5, I've run both the 32- and 64-bit versions of Stockfish 8 on Lucas Chess and can't find anyplace where Black is favored after 1.e4 e6 2.d4 d5 3.Nc3 Nf6 4.Bg5 Bb4.  Chess.com favors White by 0.18 p's:

Using various depths from 6 to 20 on Lucas Chess didn't find any significant difference:

Many interesting things can happen in the French! To say that black is often defending passively and having to find 'only moves' is a misguided oversimplification. If you want to see some dynamic and imbalanced games where black is often playing for a win you should check out 'The Flexible French' by Viktor Moskalenko. This book inspired me to continue with the opening in high spirits.

And I've heard it's quite common for computers to misevaluate openings at least in the first ten moves or so. Computers hardly ever like King's Indian positions and they hate my favorite Czech Benoni, but really there are many interesting things that can happen.

I'm talking about some specific lines (specifically endgames) in the french in which black is very passive, rather than the opening in general for the defending passively statement.

I think horizon effect might be the biggest. There are lines in the French where white might be able to create a huge attack but sufficiently down the line that the computer doesn't see it on move five

I decided I want to play the French defense as black, at least some of the time.

I've never played the French before in any non thematic game.

Is that all you have to say? I canceled my lock request for you 

Thanks for the input guys!

lol. 

Well I always disliked the French Defense, but then I saw some cool ideas for black in the Rubinstein variation (the others are too theoretical / weird in my opinion), and it changed my mind, and decided I'd like to try that out. 

The Fort Knox in the Rubinstein is also very nice looking. It seems genius how black develops all his/her pieces and solves the opening problems easily. 

Can you please show some lines?

I don't know much about the French, and even less about the Rubinstein. I just saw some 3+0 games played by some titled players, and an NM was beating up FMs and IMs with the Fort Knox and some other (main line?) variations of Rubinstein. 

its because in the french, black has a structural advantage as compared to white's space and tactical chances. When you set computers up against each other, obviously they dont blunder like a human do, which is why the comp gives black an advantage.