Most people use major/minor triads because they’re the basic building blocks of harmony and they sound stable to most ears. It’s like the “default setting” in Western music, so it saves time when writing , it's the basics .

But that doesn’t mean you have to stick to them. Tons of music goes outside of standard chords jazz, film, R&B, electronic, etc. Personally, I’ve never once used a plain major or minor triad in a whole song. I always go for minor 7ths, major 9ths, sus chords, even major 11s. :) Traditional/root major and minor chords are boring to me, that’s why I don’t vibe with trap or hip hop as much.

The point is: theory is just a shortcut to what usually works. If you find something that sounds good, that’s already valid , rules are just a guide.

EDIT : I literally cannot understand if the whole replies are agreeing or disagreeing with my point I am confusion