Because there is no alternative. And yeah, it’s expensive to have trained and highly paid people spend most of their time in a car. (I am old enough to remember when the doctor used to come to our house; that changed in my youth and we trudged to his centralized office because it was more efficient for him.)
That may be true. And it is likely that more mistakes may be made, there may even be discoveries that are better than what Tesla has. You now have global auto makers in Germany, China, Japan, and the US all aiming at the same spot. Unless Tesla was extraordinarily lucky and got everything perfect on the first try, I expect improvements (and failures) to come from anywhere and everywhere.