That trope exists for a reason. Most women go through a period in their early 30s where they're extra horny. Unfortunately, men around the age of 30 are often career-focused and their sex drive starts tapering off. It's worse in Japan, since a man in his early 30s will have a lot of work responsibilities and the work-life balance is garbage.
When we were in our early 30s, I'd joke with my girlfriend that we needed to find her some young, dumb 18-year-old she could bang on the side. I just couldn't keep up.
Nothin to do with doujins my guy. A of women ARE frustrated, because a lot of guys are selfish, even when it comes to intimacy. They get theirs and get out, women are as much, if not more sexually charged than men. They just have wires crossed and you have to know how to work with electronics... while blindfolded... and upside down.
It's confusing how they went from the tent straight to the house backstory. At first I thought "wait, they just said she was a commoner, what do they mean her noble family?" Then it slowly auto-corrected to changing the target to step-mom.