I don't mostly because it's not easy. If there were an easy way to see where police roadblocks are, I would definitely glance at it and avoid them, because I don't really like interacting with police. I've never had any particularly bad experiences, fortunately, but it still slightly creeps me out to have to go through a police checkpoint in my own country, especially absent exigent circumstances like a recent shooting, or prison break, or something. (I don't really like going through the permanent immigration-check roadblock on I-10 in West Texas, either, but no app can do much about that one.)

Although what I'd really prefer is not a separate app I have to consciously check, but integration with a GPS routing device, the way some of them can use real-time traffic info. Just let me program in a police-roadblock penalty (say, call it equal to 30 minutes of traffic), and then reroute based on the real-time roadblocks info; that way I routinely avoid police roadblocks in my daily life without having to think about it.

Most people wouldn't think to do it. But if you have a busted tail light of which you were not aware, for example, rest assured that you'll know about it after passing through a "DUI" checkpoint.