Black trading black bishop in Scotch gambit?

I've been looking at some Scotch gambit games from Black's perspective and I see that Black often gets a check on white and trades dark square bishops. Sometimes white blocks with his knight but black trades knights then bishops anyway. I was wondering what the theory is behind it because I thought black would want to keep it's dark bishop this early on.

I'm not saying it ia bad I'm saying I don't understand giving up the bishop pair especially Black's dark bishop early. Clearly there is a good reason or theory I just don't see it

In the game you posted behind 10...Ba5+ it's a tactical combination to win a central pawn. It's not just a strategic choice to exchange those pieces. If you notice well after Bxd2+ white is on a zugzwang how to recapture the bishop. Qxd2 gives the sequence has been played with the c6 knight capturing the e5 pawn, while if white recaptures the bishop on d2 with the f3 knight he loses the undefended d4 pawn.

After 14...Bxa4 black is one pawn up and it's a good reason for this combination he forced.

There is always some compensation in such trade of pieces and usually the side who forces the sequence it's the most benefit even if the profit looks small or don't you see it at all.😎

Thanks so much, I didn't notice until I saw knight takes pawn, because the bishop was hanging!