To be fair, my local Supercharger is full maybe half the time I go to it (not including before 5 am.. but I've seen it full at 6 am!), and it's been like that since I took ownership last year. Wait time isn't usually longer than 10 minutes on a regular day. On the weekend, however, the wait can be even longer, depending on the length of the line. It's also in a parking lot that gets busy and there is no good way to form the line.
Not disagreeing that it's not "the #1 reason people don't buy Teslas" but I would not call the wait to charge situation "rare and extreme." It is standard procedure here, and therefore some owners might make the (incorrect) assumption that that's the case at every SC.
Wait! What is a local supercharger? My local charger is in my garage and the superchargers are for long trips. I will say that in over 6 years and 170k miles in both my S and 3, including numerous long road trips (3200 miles in October alone) I have only found 2 incidents of full superchargers. One was in Plantation FL where all the cars had FL plates and seemed to be in the mall but I only waited 5 minutes or so. The other was when we went to the first Falcon Heavy launch and afterwards the huge number of Spacex fans waited happily at the nearest supercharger to the north. One of my best memories was each of us talking about the launch and sharing the chargers