In fairness to Tesla that is probably why they are pushing for level 4/5 so hard. It's true that if level 2 drives perfectly for a month, yet a alone a year, the human backup system is going to degrade markedly. We're not there yet, but it's coming.
That's got to open up some liability questions. You can bet when people die it will be tested in court. You could make a case that Tesla's going to be liable for many level 2 accidents in the long run anyway, so might as well go all in ASAP.