Is Tinder mostly for hookups Reddit?

You can use it for both. It used to be for hookups almost exclusively. People have started using it for regular dating, so now it depends on location. In metro locations there are still plenty of people looking for casual sex, the further you go into suburbs, the profiles are mostly looking for relationships.

Does everyone on Tinder want to hook up?

Yes and no. Tinder-initiated hookups are quite common, but the notion that Tinder is primarily about hookups is overstated. Tinder users are more likely to be seeking relationships than casual sex. Nonetheless, both studies suggest that much of Tinders popularity is, ironically, due to its popularity.