Gay dating... myth?

A problem I often run into, being a gay male who normally strikes up conversation with strangers to get dates… is that when I ask someone to get coffee, they don’t always think it is a date. 8 out of 10 times they do, but those others really bother me. A one on one meeting with someone I barely know whos sexual orientation lines up with my interests, to me is automatically a date. Upon setting it up, I even usually jokingly say “it’s a date!” I do this to try to cement the idea in their head that my intentions are to eventually get to know them well enough to ask them to dinner, and then maybe something more intimate. Why are they surprised? And if they aren’t interested why do they keep coming back?

Example:

A guy I went on 5 or 6 dates with in the beginning of this year. We went to grab beers, I paid. Me paying means, in my head, I enjoy the time I am having in a “I am interested in you” kind of way. We then went to dinner, I paid again, also, in my mind letting him know I am interested. At thee nd of the second date, we made out. To me… that means HE is interested. This repeats until the 5th or 6th date, when I finally ask him if he would like to go out with me. His response was, oh I thought we were just going out as friends.

I was shocked and said, I barely have enough time for my friends as it is… I was really looking for a partner. I cannot dedicate enough time to a new friend.

He just left, and he still contacts me ALL the time. Ordinarily I would chalk this up to him being weird, but this kind of thing ALWAYS happens. How can I be more clear of my intentions? Can anyone else see why I would be frustrated?