Over 60%[1] of these couples have sex more than once a month, and 46% at least weekly. So, hmmm, where are you getting your data from? I guess if you compare to when you first meet vs. 20 years of marriage, the amount "has gone down" (daily vs. weekly now), but that's probably more than I'd get being single at this age.

[1]: https://www.webmd.com/sex-relationships/what-to-know-how-oft...