i think some bible folk are too proud to say 'i dont know' and will run with something even if they are incorrect. In fact there have more then 1 groups of hittites identified but not identified with the group mentioned in the bible
this does not mean that they never existed though. Belshazzar and Potifer were also said to never have existed, but eventually archeology found secular evidence for them... perhaps they will eventually find the biblical hitites also