Contractor covering three counties: which towns deserve their own page?

[WebProfitLab]

I'm a general and electrical contractor in Washington State. We serve three counties (Skagit, Snohomish and Island), which covers a lot of small towns and a few bigger ones.
I keep reading that thin town pages do more harm than good, and I agree a page that just swaps the town name is pointless. But homeowners do search for a service plus their town, and one service-area page can't really speak to each place.
For people who do local SEO for service-area businesses:

• What's your test for whether a town earns its own page? Population, search volume, jobs actually done there, something else?
• What goes on a town page that makes it worth reading? Project photos from that town, local permit notes, something else?
• Have you seen a business lose map or organic visibility after adding a lot of town pages?

Interested in what you've seen work for service-area businesses.