Probably because, at heart, I am a pervert and I want too much.
Different types of women, threesomes (MMF and MFF), roleplay (including some wierd/unusual/complicated scenarios), dressing-up (including some XD), filthy talk & fantasy, trans women, outdoor & odd locations, sub/dom dynamics (mostly as a sub), sluts & GNDs, and anything else I can think of.
The chances of finding a civvie compatible with all that and more is slim to zero, and I don't think I could broach the subject even if I found a potentially suitable partner. I am not willing to invest the time and money trying to find a unicorn, but inevitably ending up with some rubbish oral and a quick fuck if I'm lucky. Even at the expensive end of the market, pay the money and (usually) immediately get what I want is a far better approach.