Well, the there are several things that pop-uo into my
head. One, they are too expensive for everyone. I will explain a little bit more of that later on in my post. Second, there is the factor of it being unpractical.
Unpractical-- I have a large family myself (currently 6 people) and something that small is unpractical for large families. I really don't think that there is much more to say other than this.
Expensive-- As I said, it is unpractical, for large families. Lets assume that my family members are all of legal driving age and each get one of these vehicles lets say for $15,000. That is $90,000 just right there! Way too expensive. I wish that they were much less. :/
One of my more recent teachers told us that he thinks that the hydrogen engine is already been made. But the companies have paid them off...