By peanuts and pennies for a significant ROI. Many places still mandate some form of coaxial or telephone wiring, which means you already have the drop points for ethernet. Even better, telephone runs are often done with CAT5e due to cost, and could easily be rewired for ethernet if it’s laid structurally in the first place.
You’re talking a $10k expense on a new home, tops. That’s chump change and easily shoved into regulations regarding new builds without significantly harming progress. The real regulations impacting housing are zoning anyway.
I can't imagine it's anywhere near $10k to install if it's done at the same time as the other electrical before the drywall goes up. Retrofitting it is so much more expensive.
You’re talking a $10k expense on a new home, tops. That’s chump change and easily shoved into regulations regarding new builds without significantly harming progress. The real regulations impacting housing are zoning anyway.