True, but it is in the nature of riots that they can break out at any time, without warning, even after a very long time of quite/peace. Some may be "small" or "local" while others larger shutting down significant parts of the city. Both are big problems if you get caught in the middle. (IMO, the safest response is to hunker down, but that is not always an option.)

I was caught in 1 major urban riot: Washington D.C. in 1968 and had to bug-out as the college dorm was shutting down and kicking us out. It took some creative thinking to get out, and of course, I didn't have a bug out bag, or even a SAK (expelled if caught with a "weapon" in the dorm.)

IMO, the infrequency of riots should not preclude them from our planning for your urban bug-out or bug-in plan/kit. Unlikely event, yes, but serious enough to justify planning and thought. I think most of our survival planning is for unlikely scenarios that we hope will not happen, but experience says can and do happen without warning.