My assumption is having a long term partner with out having sexual intimacy is fairly uncommon, understanding sexual compatability for people looking for a long term partner is a probably high on the criteria to sort by.
IE hard to understand compatibility with out the deed.
That said I agree the perception is that Tinder isn't socially known as the place to find a long term partner.
Call me old fashioned, but the ability to approach people in the real world about your interests in a socially acceptable manner may have less potential surface area but is probably a higher success rate for longer term relationships.
Also hard to judge how you'd be in a relation with someone beforehand, even if you already know that person well.