Firstly ICANN had a black list of TLD labels that is wasn't going to allow anyone to apply for because they know they were likely to be in use.
If they looked at every "bad" TLD name that hit the root servers they could never add any new TLDs.
Having awarded contracts for TLD's they are try to minimise the impact on those labels that didn't make the black list or that they were unaware of.
Actually they do own and run one of the root servers. The company I work for owns and runs another of them. I submitted arguments, as a private individual, to not expand the root zone when this was being mooted. That all being said they are the legitimate party to decide what gets added to the root zone.