We have both "Why *they* said no", as well as "Why *we* said no" stories:
After seeing our face photos, the other woman quickly 'noped' on us because Mr Bluebird -- apparently -- looked exactly like the other woman's brother. Mr Bluebird wasn't actually her brother, but she said the resemblance was too great to overlook.
The situation where We said 'no': We met up with -- unbeknownst to us, as we hadn't met them before -- the parents of our Daughter's Significant Other: We were going to meet them the following weekend for the first time when we helped our kids move-in together. This wouldn't have been a problem, but we had never met them before, and while we were having an introductory chat over drinks, they let us know that they were quite "Open" about their involvement in the LS: Their friends, family, and even kids knew they were swingers.
And if their kids knew, that meant our daughter's SO knew. And -- by virtue of their relationship -- our own daughter would know about their activities. And that was just *too close* for us to consider playing with them -- We're not 'out', and wanted to remain that way.