They don’t “visit.” They’ve been here the whole time. More have come since the first arrived, though they just drift around in their (living machine) vessels, observing everything.
Most of them spend their entire lives in their pseudo-embryonic sack, a very rare few actually get out and walk around, so they don’t really compete for space or resources in the same way humans would.
Their technology works largely through the mind, so they can literally observe the world through your senses while a million miles away. There isn’t a thought or experience you can have in your own mind that they cannot perceive in greater quality and detail through your own senses.
While altruistic, they are wary of humans. Humans are unpredictable, unreliable, and frankly a danger to themselves and others. There is little incentive to “meeting and greeting” modern Man. Humans are not the most endearing part of Earth.
Oh, btw, there is a secret war among humans. Those who have the power of thought control are running a secret governance of power against the rest, so it isn’t like you’re really aware of or speak on behalf of your own humanity.
They continued chomping down celery tops and coriander.
One of them likes to watch planes. It sits on its hutch in the afternoon watching planes from a local airport fly away, more interested in them on days when the wind's blowing such that when nearby they're taking off rather than days when the wind means they're approaching. The other one doesn't care for planes, but stamps whenever a wasp's nearby. This second one also likes to observe, then crush with a front paw, any ants it comes across or that come across it.
Remarkably human behaviour, though I know not what they think. Is it curiosity. Is it fear? Is something in-built and there is no 'thinking'? And what of us? Do we really comprehend? An Area51 alien is to me as a flying celery-rabbit on a magical boat with radish tops for wings is perhaps to these rabbits, if they've ever thought to imagine. They do seem to dream. That is, it's completely within bounds of their known reality. As outlandish as the very real, lived, imaginations of a schizophrenic delusion may be, and my observing it based on my 'norms', it's still somewhat based on the individual's experience, or imagination, of their reality, their experiences.
Perhaps there are aliens. Perhaps they exist in differing dimensions. Perhaps they exist as stars blinking to one another, perhaps they exist in my underpants or in fact are my underpants, what do I know, we are all in our (bounded?, there is always a bound...) existence, as Spinoza pointed out, of "Substance, its attributes, and modes".
OTOH, I think it's highly unlikely that UAP's or UFO's - or whatever you want to call them - are alien spacecraft piloted by intelligent extraterrestrials, coming to visit Earth, abduct and probe random humans, mutilate cattle, make crop circles, etc.
That said, over the last 30 years or so, as we've discovered more and more "potentially habitable" planets, some closer to Earth than the ones that were previously known, my skepticism on "alien visitors" as diminished very slightly. But it still seems unlikely to me that any intelligent life that exists, is close enough, or has the means to travel interstellar distances quickly enough, to permit tourist visits to Earth.
But they aren't anywhere near Earth, and it takes too long to travel between star systems to make such a journey worthwhile.
Read up on the Fermi Paradox: https://en.wikipedia.org/wiki/Fermi_paradox
I'm leaning towards the "aliens exist" opinion, btw.