>'That's (supposedly) because a ticket for anything less than 10mph is simply not worth it for the cops.'
Depends on your cops.
I've witnessed tickets for 5 over (40 in a 45), 4 over (49 in a 45) and a stop, thankfully without a ticket for 1 over (31 in 30).
I'm given to thinking of it as a lottery. Someone is getting pulled over, today me, tomorrow someone else. I'm just glad I haven't had a case of 'marijuana smell' for 10 years or so.