A lot of folks who have static websites aren't technical and invested thousands of dollars for a WP website. If their site already runs, you wouldn't be providing anything.
...unless they have to pay noticeable money for WP hosting due to serious load, or were bitten by security problems.
A free business idea: write a converter from WP to Jekyll (or Hugo) that converts 95% of a typical WP site right, sell total conversion services, maybe reselling hosting, too.
I have several WordPress sites (mostly "abandoned"/no longer updated) that I would love to convert to static sites. I would happily pay a decent sum for a tool that could completely handle that conversion/migration.
I used https://de.wordpress.org/plugins/simply-static/ to convert a WP site with 10.000 pages. Took about 60 minutes so i had to increase PHPs max_execution_time. I also tested some other plugins before but most don't worked for me.
I had to turn off HTTPS for the generation time and reportet it as a bug to the developers.
A free business idea: write a converter from WP to Jekyll (or Hugo) that converts 95% of a typical WP site right, sell total conversion services, maybe reselling hosting, too.