I would have to say because while they do produce relatively clean power, it is extremely dangerous and overly harmful should one "melt down." Some people believe the reward is worth the risk, others do not. It is more a matter of perspective - are you near the nuclear power plant or not? If you are, chances are you won't like it - on the other hand, if you are not right hear the power plant you might like it more. I hope this helps!
P.S. - If you think I did a good job I would love it if you went to my YouTube channel to see if I can help you more there. I am just starting out and don't have much time to record, but I would love to have some user-submitted topics! Here is the link: https://www.youtube.com/channel/UCG0zQcSsxZ2mu-OnZRdI2-Q. I hope to see you there!