It can also be a dominance thing as well. Telling someone you are going to plug them and then take them to dinner or somewhere in public can get a fast blush on the cheeks. Having to submit and bare their ass is very nice.
Yes, I've had the pleasure of being told by a trusted Domme partner on a couple of occasions to insert and wear a plug when we were going out somewhere. If you enjoy that kind of D/s dynamic, it can be a nice satisfying thrill. I'm a switch and enjoy being Domme-ed at times. And as others have said here, part of this particular thrill is knowing my Domme partner and I are the only two people who know she's given me the request and I'm wearing the plug as ordered under my clothes, Makes for an entertaining evening together at the restaurant or movie or shopping spot.