I'm not sure I understand the question fully.
When one of my girls gives me a massage, of course I'm nude as are they. It's a normal part of the whole experience when your with someone you've done much more with.
Sometimes it leads to other things, but not always.
A naked massage can / is one of the many good things done in foreplay...whether he massages her or vice versa or preferably a join/mutual massage experience.
I have never gone for one but I sure would love to. It looks like a hot and sexy time. Not sure the spouse would like that but I sure as well would.
Everyone naked. Masseuse and all. I with a female and she with a male. Why not make a party out of it!
I suppose I can understand why this would not be for everyone. But I can't see any reason not to seek it out if you are having fantasies or otherwise are interested. I like to edge & dabble in Tantric sex. Massage is one aspect of this. Have a partner who has a number of times engaged in full body massage with me. Usually mutual. There is always a sexual component to these sessions, but some times we don't go beyond some nipple tweaking and brushing fingers over our genitals, or it can go a bit further, or all the way to full sex and orgasms.