It was harassment and country-of-residence profiling (driving while Canadian, though admittedly it was also a major corridor for pot smuggling at the time). Crooked police cultures can set in for all sorts of reasons.
Additionally, all around MSFT campuses in the old days there'd be cops waiting to catch exiting employees going 36 in a 30 (exactly 5+ over) at the end of the month to fill their quota.
There used to be a host of lawyers on the Eastside who specialized in getting rid of traffic tickets for MSFT employees on technicalities. It was cheaper than having your insurance jacked up.
I got a traffic ticket every 6 months or so in WA (all of them for 6 miles above in a residential, because I drove like an old man even when I was young). Since moving to CA, in almost two decades I've gotten exactly one for rolling a stop sign. My driving habits haven't changed.
All that to say traffic enforcement is a relied-upon income stream for some places in the US.
Throw in waze and you're in a situation where you can basically cruise at 90 for a long distance vs. 75. Escort or V1
For these kinds of stops, where they were waiting on side roads for you drive by, a radar detector might not even help much ?
I did have friends with detectors for highway driving, so your suggestion is solid. I wish cars had them as options like leather seats :-)