A town page is a page on your website about your work in one place. Not a list of towns, and not your homepage with an area mentioned. A page whose whole subject is roofing in Wakefield, or drainage in Hanley, written for somebody who lives there.
Why separate pages at all
Roofer in Leeds and roofer in Wakefield are two different questions as far as Google is concerned, answered with two different sets of results. A homepage saying across West Yorkshire is competing in both with nothing specific to either.
There is a human side too, and it matters more. A homeowner who lands on a page showing a job two streets away has already decided you are local. That happens in about two seconds and nothing else on the page buys it back.
The bar a town page has to clear
Real local detail: the suburbs and villages, the housing stock, the stone or brick that is common there and what it means for the work. At least one photo of a job you actually did in that town. A tappable phone number near the top. Something a stranger could not have written, such as how quickly you can get there from your yard.
Pages made only to funnel people somewhere generic are what Google spam policies call doorway pages, and forty of them built by find and replace is the fastest way to make a whole site look cheap.
A worked example
A builder covers five towns and starts with the four he has photos from. Each page names the villages inside that town, shows a job there, and says how often he is in the area.
The fifth town, where he has never actually worked, gets no page. He would rather have four pages that earn calls than five where one brings enquiries an hour away that he turns down.