"Often endgame" and "quickly"?
Could u give variations please because I don't think Alapin is supposed to reach endgames, pretty rare in my opinion!
However, u are right, Alapin is a very practical (and reliable) way to play against sicilian! Easier to learn and play than open sicilians.
I didn't mean endgames in the book moves, but the open positions can lead to further exchanges.
The c3 Sicilian leads to positions similar to after 1e4 e5 or 1 d4 d5, open positions as you might get from the Tarrasch Defense, Petrof's Defense, the Berlin Defense, or Alekhine's Defense. I am better at an open game without a lot of maneuvering and which may reduce to an endgame than with some lines of the Sicilian open defense.
I don't like many of the Sicilian lines. However, c3 seems to lead almost always to 2 pawn exchanges in the center and can get to the endgame quickly. I don't think it is easy for black to avoid that. Maybe that is why it has become popular.