- Many of them are murderous.
- Many of them are monsters.
- Some of them are shape shifters so would you know who was what? Probably not and disastrous consequences will inevitably result.
Do you really want any of those turning up on your local High Street? I think not!
- If their magical qualities worked in this world, they would unleash chaos. Why? At least one character wouldn't be able to resist the temptation to impose their will on humanity. See Doctor Who for more specifics on this. Where you get aliens, you get power crazed aliens too. Mind in fairness, that does apply to humans as well. But it is probably best it is just us on this planet doing that. If we had aliens from other worlds muscling in on this, I don't think the planet would survive for long.
- Having to explain our technology, our laws etc so they could survive in our world would probably be a long and tedious task. I strongly suspect it would be impossible to persuade Mrs Bennett of Pride and Prejudice fame that daughters don't necessarily need to marry to have a fulfilling life! And that only names one example.
- The pleasure of reading is to escape as I mention in my other website, Fairytales with Bite. How can you escape when those characters are here? Besides the advice is you should never meet your heroes.