The problem with projectors is that they can't display black: they're shining light through a filter, so they can't produce a true black, and the contrast ratio isn't that great. For best effect, you need an extremely dark room. With an OLED screen, black is absolutely black, because black pixels simply aren't lit up at all, and you get better contrast ratio than a projector. As a bonus, you can even watch it with the lights on.

Obviously it depends on your projector/screen choice but it’ll probably be cheaper, too. The portability is also nice.

If I watch a movie by myself, I would choose my $500 27" 4k monitor connected to proper speakers/headphone over a $300 55" TV without external soundbar any day. Most people probably will choose the opposite, which I totally understand.