The problem is: a Tesla is radically different from any other car. You need specialized knowledge (especially in HV distribution) to properly repair it, and most likely also ultra-special tools, and from what I've heard (eg https://forums.tesla.com/forum/forums/replacement-parts-why-...) spare parts are extremely hard to come by, even for official Tesla shops.
So basically you need a massive network of official shops and dealers in order to assure the customers that their damaged/broken car is going to get fixed... and that's where BigCar has an advantage: all they need to do is to train one or two employees at each existing shop/dealer in how to service/repair an electric car, and they have the entire country serviced. Tesla on the other hand has to build the stores, hire and train personnel on their own... and that's a significant hit on capex.
Not to pile on here, but I think this is one of the things that many Europeans underestimate with regards to Tesla in the US market. If Tesla can continue to sidestep the traditional dealer franchise network, and their lobbying efforts, while scaling, I think this could be one of their biggest advantages going against the established auto companies. Unless you've been subjected to it first hand I think it's difficult to understand just how awful the US dealer experience is. From what I've heard the transparency of the Tesla buying experience is a consistent selling point.