We tend to try to predict alien behavior basing it more or less on our own, 10000 year-long history. If intelligent life that travels the billion-old stars actually exists, I doubt we would be able to put their intentions and modus operandi into words with our constrained ideas and limited, lonely planet vocabulary.
Of course, for most of that history, the default result of a more technologically advanced culture meeting a more primitive one was the former immediately enslaving or committing genocide against the latter.
And let's be honest, if the Sentinelese were sitting on anything worth killing for, they would be long dead or "civilized" onto a reservation by now.
Here we're talking about meeting a culture not made of human subjects. We know nothing. When they're able to cross interstellar space we're unlikely to have anything they'd want. They'd be so advanced technically we might not even detect them given our limited understanding of physics.
The thing I do see an alien species could want from us is our capability to understand a blueprint and to reassemble them physically from transmitted information. Because that is how they might travel between galaxies. Their assembly, I hasten to add, would be a rather stupid thing to do on our part. If we want to live. But we might do it anyway because we're curious.
How are the scenarios of brute predators, noble protectors, or imperial fleets any more worthwhile to consider than those of the incessant replicators? My answer: Because our culture likes that kind of tale. Because we project our predatory and social features onto an unknown.
So whenever somebody explains phenomena like blips on a radar with an alien species that happens to be eerily similar to us I think of how people made god in their image and either rail against the blatant human-centrism or just disengage.
