I have thought this same thing.Purchased my 2015 70 a year ago and strictly FUSC probably every other day. No noticeable degradation. My fear is if/when Tesla Superchargers will be available to all brands it will make it nearly impossible to find a space. I will have have to install and charge at home and incur higher electric bill.
But then as others have pointed out, Tesla is pumping out more EVs than most and so this “concern” of filled chargers is happening regardless. If by opening the network, can add more funds to increase the network, the better.
But I do think there will be growing pains with some people taking up two spots due to the cable position and people pulling into non-shared locations. Will be a learning curve.
Overall though, I think this will be a good thing for the network.
I suspect there will be more people buying non-Teslas and using the Tesla network but Tesla will still sell very well due to pricing power.