What's actually having friends with benefits like?

My brain is stupid so I don't think I explained/asked this this properly.

A quick story: I knew a girl that I was friends with (obviously) and we had a somewhat innocent but intimate friendship that I guess would fall under FWB, It started off with hugs and cuddling to, kissing and making out, to practically eating to my heart's content between her legs, but although with all the intimacy to try and progress the relationship out of FWB, it stuck as that and I never got to have her, or the fact that some people will only want an FWB and they will just do stuff litterally the second it's mentioned, without the whole romance feelings growing I don't fully know how it works

What is it like to TRULY have one, cause I'm pretty sure mine wasn't fully FRIENDS only, but I wanna here some other perspective.