Because people prefer familiarity over the unknown.
It’s not a new phenomena, as there have been remakes and sequels for almost as long as there have been movies. It’s also not unique to movies as far as sequels go. Readers begging for sequels to popular books are the bane of authors everywhere.
Just enjoy what you enjoy and ignore the things you don’t. For every remake or sequel there’s an original movie produced by a small independent studio somewhere that’s desperate for viewers.