I wonder why the WOW! signal
was never truly classified by scientists as our first contact by extraterrestrials?
It clearly wasn't from a natural source according to most journals I've read on the subject.
Because we don't know if there are extraterrestrials (close enough to send that signal). The WOW signal in itself is not significant evidence that there are aliens (it can
be explained by natural phenomena – even if it would be difficult, aliens are still more extraordinary at this point). OTOH, if there are aliens that close, it is more likely to have come from them than from natural sources, as it does resemble what an artificial signal would look like just like you say. So the only thing the WOW signal does is refute the argument "If there are aliens, why we haven't heard from them yet?", but that argument was falacious to begin with, so the WOW signal doesn't change much there either.
It's creepy in a way. If we have alien neighbours having powerful radio transmitters, it is close to certain that we have received a signal from them. Yet we are no closer to knowing if we actually have such neighbours, or if such species exist anywhere in the galaxy, and even in the universe. (I'm personally sceptical about aliens in our neighbourhood, but I am positive about aliens in our galaxy, and somewhat close to certain about aliens in the universe – though in the last case we'd never hear from them.)