They are excellent negotiators and traders. If you need something like an ionized plasma channel or even a prototype phase cloak, the Ferengi can find it for you.
I own a Morn action figure, have Mark Allen Shepard's autographed Morn card as well, because of his character being a Cheers reference. I even have a metal die cut Morn card somewhere I think.
TNG Ferengi were more interesting. DS9 they just felt like filler B characters and any Ferengi episodes were inane. But then, I think DS9 sucked.
I mean, the Ferengi were a total flop. They were meant to be the big bad guys in TNG but their appearance was deemed too humorous. That’s how we got the Borg - needed a big bad guy.