Should contractors write blog posts?

Only if the posts answer questions your customers actually ask before they hire. A post explaining what a roof replacement costs in your area, or how to tell a slab leak from a running toilet, can bring in people who are close to calling somebody. General filler about the history of plumbing brings in nobody who will ever book you.

For most contractors, blogging is the last thing to do rather than the first. Your service pages and city pages earn far more work per hour spent, so build those out before writing a single post. If you are still missing pages for services you sell, that is where the time goes. Once the foundation is there, a handful of genuinely useful posts each year is plenty, and each one should link to the service page it supports.