Got to say that in 7 years of punting, in parlours, incalls in hotels, incalls to private house, outcalls to hotels or to my house; never got under the sheets with a SP, or even had the SP hint that she wanted to get under the covers. For the majority of them it's never crossed my mind, although there's a couple who I've had longer bookings with, 2 hours plus, who I wouldn't have minded getting under the covers with whilst I awaited for the wood to return.
However, with civies - every single time they start off under the covers, the first time we've fucked. But then civies will always do owo, think it's rude to do anything but CIM and never complain - well not much - if I cum in their hair when giving them a facial.