Little Green Men statues in Little Green Man Store Command

I don't doubt that aliens have visited this planet and likely continue to do so. I do think that they avoid the local indigenous species on the planet because they are prone to paranoia, out of control behaviors, and are generally messy creatures. If they are witnessed they are only done so from a distance and likely when actually some contact is established it's only with a single yokel who is best left to yammer along that he or she had first contact through the fog of alcohol on their breath.

I fervently believe that the government has suppressed evidence of alien visitations in the past, but I congratulate them for it. People would lose their collective marbles if the world was clearly not alone in the Universe when it came to life. We live a comfortable fantasy-life that we are the only creatures in the entire Universe that are sentient. Notice I didn't say intelligent, you can have sentience without intelligence. Look at politics.

I think a good portion of the existence of aliens is predicated on the sheer number of stars, planets, and of those the habitable ones. Then you factor in natural curiosity and the sky has to be teeming with alien life and a lot of it should be zipping around Earth curious about our infant species.

I don't think we are ready for first contact. We are too wound up in religion to ever be allowed off the planet. For the time being, we are really a leper race, our behaviors are too erratic and we are too immature to make first contact and be respected afterwards. We'd likely militarize the entire endeavor and make an utter ass of ourselves as a species.