Richy,
what you're talking about is actually something I hear a quite often in my interaction with clients, and there are several reasons for that. The first reason has to deal with body mechanics. When trans girls start transitioning him taking hormones it precipitates money at physical changes, chief among us that is the thinning of the skin. As we move along our transitions, our skin things out and picks up a little bit of a translucence to it, in addition to that and also become significantly more sensitive. While in cases this may not be an issue, for some individuals that sensitivity is extremely high. So when it comes time to do the deed, that extra little bit of touching can be enough--while feeling good--to be uncomfortable or possibly painful. I can't necessarily speak for other girls, because I am not them, but I can speak from my own experience is. There have been a few occasions where what you described, is exactly what happens, though that's few and far between.
The second explanation has to do with the demand. Again, judging from past experience, the vast majority of individuals that I see you want to actually see what happens. So having that little bit of "Stand off distance", if only an inch or two gives just that bit of distance where you can see what's going on, and have the get the same and result that you're looking for. Also, please consider that a lot of people are not as hygienic about things as you may be it, and on top of that the specific provider is not going to be aware of that and less she physically see is you do such. There are many individuals, if you coming from TER that I have noticed, Who put significantly less preparation or thought into it as you and other members here. There's also the issue of things outside of cleanliness and hygiene. Even though somebody may have taken the appropriate time to do things like brush their teeth, or shower, those things are not going to stop the transmission of STI's, and I doubt anybody wants to take that risk and end up with the gift that keeps on giving, especially as that's a career ender for us.
The final reason is kind of a combination of mechanics and demand. Again, a lot of you guys want to see what happens when we pop. With that, there's also constraints of biology. trans girls that are actively taking hormones aren't going to have a huge end. Well I'm sure that may be upsetting to some individuals, it's the reality of transition for any trans person who is doing such medically; our bodies just aren't capable of a whole lo and coupled with the demand to be able to see what happens, that little bit of distance allows that to be the case.
I hope the answer is what you were looking for, and if not feel free to send me a private message and I can explain further.
finally, if that's something you're looking for, ask… The worst it's ever going to happen is a provider telling you no.