Peacock puts a ton of the Classic Monsters movies up in September like clockwork, so they can generate online headlines about "30 classic monster movies just got added to streaming!", then takes them down again after Halloween passes. It'd be nice if they kept them up year round, but titles that are always on your service don't generate coverage.
I eventually just bought the complete 30-film Blu Ray box set, which can often be had for $70 on Amazon. Very comprehensive, though because it's assembled out of individual character collections you end up with three copies of House of Dracula.