I've always found this argument a bit bizarre, because in my mind any time travelling device would work via a pair of machines: a sender and a receiver. So nobody could come to the present simply because there's no receiver yet.
The reason we haven't been overrun by tourists because there's no stop in this time period.
>I've always found this argument a bit bizarre, because in my mind any time travelling device would work via a pair of machines: a sender and a receiver.
Were did you get that impression from? Not most Science Fiction or Physics, because neither postulates such a thing.
Actually the only vaguely plausible-ish (though by no means convincing) designs I've heard of for physically realisable time machines work like this. You do some horrendous things with spacetime curvature and you get something that can send you back in time, but no further back than the point at which you constructed your horrendously curved spacetime thingy.
Paul Davis has a short book How To Build A Time Machine which does it this way, if I recall correctly (it's been a while since I read it).
As for physics, you are mistaken. The only kind of "time travel" that has any basis in physics is the one using Closed Timelike Curves (which is what the article is about) and those are limited to the time the CTC was created in the past.
So, in fact, this is a very good reason to reject the argument of "If it is possible, where are the time travelers?".
The reason we haven't been overrun by tourists because there's no stop in this time period.