More than 2 million people live in unincorporated Harris County with no city police department to call their own, so they often call constables instead.

The office of constable may have made sense back when Texas was a sprawling frontier. Instead, constables basically now run their own little personal fiefdoms.
Maybe it’s changed, but I also seem to recall meeting some constable or constable deputies who didn't even cary a firearm...probably that wasn't Houston though.