It appears somewhat caused by the fact that the “do it yourself experience” used to be a very inferior product, which drove people to find a partner, even if it meant significant compromise.
Now, you’re one search away from stimulation that might actually make it better than what’s available to you in your local community.
What may be shocking to some people is that this phenomenon applies to people of any gender, and is likely a contributing factor to the “incel” phenomenon (some of the more awkward among us used to benefit by being “the best available local option” so to speak).
But ofc no-one wants to talk about it because it’s a bit gross to do so.
[0] https://www.psychologytoday.com/us/blog/sexual-intelligence/...