1. e4 e6 2. d4 d5 3. exd5 exd5 4.c4? What's your opinion on this for White?

List the pros and cons if you can. 

I believe it's a good surprise weapon against French Defense players but why is it not that popular?

I wonder why the Panov Attack of Caro-Kann (e4 c6 d4 d5 exd5 exd5 c4) is more popular though. 

The real problem for black is he allowed white to have double pawn on e file and open f file . Black should allow white to capture the dark squared bishop instead of moving knight to d7 he should play Bca7 so if white trade of black bishop also he dont have double pawn + a open f file...after this game will be slightly in favour of black...

There is no double e pawn and open f file? 

I think Korchnoi came up with that line.

It's OK. But probably not any better than anything else in the Exchange French for White.

I like how it turns the game from positonal to tactical though but I guess there could be better options for White that's why it's not popular. 

The main problem black can equalize easy.

There are many ways for black to setup their pieces and they equalize fairly easy.

I think people like to teach kids to play that because many kids will fall for tricks involving the pin on the f7 pawn, and the white player need not know any theory.

Caro Kann Panov Attack has an IQP too for White though. 

If your pieces remain active, the IQP is a space advantage and an anchor for your knight(s). If you stall out, it's just a target.