I would disagree that runners expect all races 5k and longer to be certified. Where I live, there is a summer XC series, the venue has 3 different courses that they rotate. It's advertised as 5k, but although the courses are close none is actually 5k. Entries in that series are very strong compared to local races in general, and every year they get more runners. That tells me runners can be looking for other things that they're going to value more than course certification. (I know, it's XC, not certifiable...just responding to the statement "all 5k races and longer".)
As for road races, as a runner and coach while races on certified courses certainly bring more credibility to the table, there are a lot of races around here that are generally considered to be accurate. Those I'll put in the same category as races on the USATF list. Some people that put on races, I know they care to get the courses right, so I really don't mind if they're not actually certified. On the other hand, there are a couple of people who put on races around here whose reputations are that their courses are never the right distance, so for them even if they got a course certified I'd wonder how they were going to mess it up.
From the race producer perspective the company I work for has some races that are certified and some that are not. All the races we produce are measured by the USATF protocols (by me), it's just that for some we're playing around with the exact start/finish/course so we might not file the paperwork until we dial in exactly how we want the course to be. Sometimes that takes a couple years. Our fastest growing race is a half marathon that is not on a certified course. I'll probably file to get certified soon but so far the fact that we're not on the USATF list has had zero impact on registrations or racer feedback.