Fritz Gambit attack for black

I was wondering about d4 g5 e4 Bg7 Bxg5 c5 and pressure on d4 square😀

I think it's dumb. Why does White have to take on g5, and let you play c5? Why can't he leave that hunk of crap there and make you suffer for the rest of the game in a modern where you have just played ..g5 instead of the more tight ..g6?