Why does nearly every opponent move a knight 2nd/3rd move?

Can anyone explain why in almost EVERY game that I play, my opponent will bring their knight into play on the 2nd or 3rd move. I NEVER play like that, I always open with the queens pawn up 2 and then make a diagonal line of pawns that protect each other, most of the time it confuses the opponent as they're expecting to play someone who also moves their knight 2nd or 3rd move, and therefore don't know what the hell to do. (I usually tend to quickly remove their initial knight with a knight/bishop exchange, which a lot of the time they take with a pawn and therefore create a double pawn line which is never a good position to be in).

Furthermore, continually moving a knight away from attacking pawns at the start of a game (because they've brought it out with no protection) is also never a good idea because it greatly increases the chance of the knight just being blundered.

So for the life of me I really can't understand why anyone would choose to bring knights into play so early in a game in every game.

It is because you should develop,castle and then attack. But you can also play the bishop after opening the e4 pawn,like in italian. Playing knight on the 2nd or 3rd move is upto players choice. Like I recommend bishop first.

Not much attacking can be done though when an opponent faces a wall of pawns that are either stacked horizontally or in zig zagged lines that protect each other. Though bishop diagonal to a rook is the better move as it doesn't open a knight up to an almost immediate bishop/knight exchange (and potential double pawn line) and opens up a better attack on the opponent's rook(s) (if the player 'forgets' that the bishop is there).

Because knight controls two center square at once compared to bishop who can control only one center square.

Plus Knight has a very safe position than bishop who came out but can be attacked by a pawn.

can easily fork opponent if you place either knight and either side.

Opening principles: control the center, develop light pieces and make your King safe. The fastest and more natural way to do that is something like e4 e5 (control the center, open diagonals for the bishops). NF3 Nc6 (attack and defend e5), bishops  somewhere on the diagonals, castling.

I am not saying you should castle as fast as possible. But if you don't want to have your King stuck in the center, you will  have to move a knight and a bishop very early... so why not almost immediatly ?

One of the biggest opening principles is to develop minor pieces, generally keep heavy pieces behind and flexible. 

The knight is more flexible than the bishop by nature, so bringing it out first is preferable. You can decide where to put your bishops after you have at least one knight out. Also the knight blocks the king from castling, so you're usually gonna have to move it anyway.

Your pawn strategy is often refutable: good development and pawn breaks smash open the position and the opponents development advantage becomes overwhelming.

My guess is that matchmaking system can be biased towards searching an opponent that somehow correlates with your playstyle patterns. In my games, like ~80% of them, i get fried liverers or Qh5 abusers and made whole topic about it aswell but with slightly different points of concern

I don't think so. When I play at my peak blitz or rapid ranking (over 1100), I play essentially against classic sound opening. But everytime I go down around 1000 after a losing streak, it feels like people only play the last "win in 10 moves" trick they saw on the internet.

And these game are not easy. You know the opening is bad but a single mistake   and it's over. But these players just can't really go over à certain level, and you see less of them once you play a bit better. 

Because its a very good developing move lol

Well, actually, I checked your last 10 games and found none of those.

Lol. 3rd, 4th especially, 7th, 8th one is Q abuse (h4 not h5 cuz hes black but its essentially the same behavoir). Okay in selection of last 10 games i had 50% of normal games and only 2 (10%) of them were straight up abusive. Your right, its not the numbers i told here and now. But last 10 games is not a representative amount either and it is not 'none of them'.

None of those games are even remotely close to what you are talking about. Only one opponent move that queen at all, but only after (and because) you weakened the e1-h4 diagonal, and traded it immediately.

Only one opponent moved the knight to g5, and only after you forced the knight with e4 to move from f3.

It weakens nothing, he was not forced to do that at all, as you mentioned, because noone else did that in other games. He mindlessly excanged bishop just for the sake of exchanging and then attempted classical Q rush. There is basically no continuation of his Q move in combination of anything that could possibly create a mating net because all his pieces are literally not developed. If i wouldn't block with my Q ( _that is also does not force him to take it_ ), he would go default nom-nom-nom garbage. And even if it would be the case, early Q is an abusive strategy targeted for fast rating farming rather than actual quality play.

In knight game, all happened only because he had clear fried liver agenda but he haven't seen that i can block bishop with pawn, well, because of that agenda. He failed with fried liver and continued with Qh5 abuse instead of stepping back and playing normally.

It's funny you talk about playing normaly with that f5 move

What's wrong with f5? I want to take my bishop out, move my Q behind it and do long. According to analysis, f5 is a slight inaccuracy but nothing extraordinary. Idea that it weakens something blunder-like is delusional. It is more like a litmus paper to detect Q abusers.