In response to us not having hoover cars, if they did make them they wouldn't release them yet, they want it to look like a really slow transition, so people don't question it like, "Hey how did we get the technology for that hoover car?" and then another person will say "Something fishy is going on here!" Inevitably people will start to talk and yeah we'll have a crisis on our hands because everyone will eventually realize it was aliens, and people knowing about aliens probably won't help us keep the earth clean or green or whatever because on one hand you'll have the people who don't care about the earth because hey if there are aliens they will eventually come back and like teach us their ways and we'll blast ourselves off this rock and find a new home. And the other people will be actively trying to make our planet worse so that the aliens don't want to come here and take over to use our natural resources.
Yeah the government is playing it's cards right.