Why in the end i always end up as friends?

So, might sound strange, but I recently realized that most of the times I (M, 19) end up friendzoning all the girls. Even if I like them at first, in the end I usually realize that I think about them as a friends, not relationship partner.

I love them as my friends, but when you see all your friends having relationships and only you're alone... Well, let's say after such evenings I usually end up sad AF.