Why are so many crazyhouse players sacrificing their knight in opening despite no advantage?

Yea if you look at lichess opening explorer you will see it's quite a successful opening for Black. There are three reasons:

1) A knight is worth about two pawns in crazyhouse so it is a sacrifice but it opens the f8 bishop with tempo, and Black gets faster development than White despite playing second.

2) The pawn can often be dropped on h3 defended by the c8 bishop and help launch a lethal attack on White's king.

3) When Black castles, the extra pawn on f6 gives added safety to Black's king. There are no attacks possible via e5 as for example in the French defence or if the knight had been moved.

Wow that's a lot of advantages I didn't see, guess I should get better at crazyhouse lol
Thanks for the great explanations!

There's even a fourth reason I never thought about before which is

4) Black castles quickly and can attack White along the open e-file before White has had the chance to castle e.g. lichess.org/HSVH811h

It's a tactic

I mean that’s White‘s main idea.

Xf7, Ng5+ and something flies into f7.

I see this more of a bughouse opening, but it's also playable in zh and easier for black. It's a solid structure which prevents white piece activity avoiding Ne5/Ng5/Bg5 and Bc4 complications. It also allows for early castle.

For white, it's not always so clear how to develop the pieces. Probably white's best plan is to stay as solid as possible, wait for black to overextend pieces and then counter-attack. I've seen some newer players not know what to do with the Nf3 knight after black plays p@e4 - they don't realise sometimes it can go to Nh4 and then Nf5 later.

An example of the strength paradox. The N is worth more, but for structural reasons it is hard to find a square to put it without getting pushed around by the weaker pawns.

If you can avoid getting mated in the opening, you have a fighting chance. This opening has often delayed me getting mated, and so I play it.

just to make you think we're crazy.

Just because we're crazy(and that's why we play zh)