While there are specific sites for BDSM dating with more nuanced optoins, the ads for generic dating sites are all very "tame" and try to not deviate from the perceived norm too much (= "find a partner, have a happy family" type messaging)
The reason is that if you do, it's virtually impossible to get included in Ad networks and App Stores. So you naturally see only dating ads catering to the very conservative viewer.
Example: A BDSM dating site got banned from Googles Play Store after including a background image of a simple leather whip. [1]
[1] https://twitter.com/devianceapp/status/1384015666185834501