You have pretty much answered your own question. "You do not hook up...". By far, most guys using the apps are out there solely for the purpose of hooking up. Hence, the plan ain't really working
Like it or not, you are on the dating market now. There are guys out there looking for all sorts arrangements starting from friends with benefits, over to FBs and some dudes are really looking for someone to tie the knot with.
Very, very few guys are out there saying that they really want a serious LTR here and now. You are chasing a unicorn. Mostly because such relationships are NOT found. They are made over a period of time.
By saying that you are not into the hook ups, you are signalling to most dudes out there that you are a sexually negative guy who is more likely to make an issue about putting out than not. Now, this is probably not the case, but this is how your attitude is being perceived by a number of possibly qualified guys.
Time is precious these days, so guys are moving on very swiftly to the next cool looking dude. If the sex part works, they'll probably try to see if there is any level of compatibility, so that something more lasting evolves...Deny them sex as preconditioning it, and you are in for a long, lonely and disappointing ride.
Consider giving yourself a break here...