What's the purpose of those? There are countries where this pay is acceptable? Can't really think of a reason to attract attention this way.

They usually want to build up reviews / ratings on their account so that later on when they have a lot of 5 star reviews they can raise the prices.

You do a great job on crap jobs to get a good rating so people will look at your proposal for decent jobs. A friend did that for financial modeling jobs on Upwork after doing a CFI course and was making $50 an hour within two months.

And yes, there are many countries where a $1 an hour job would get a lot of applicants.

The way the parent phrased it, I assumed it's the other way around - $1/hr job offers are being sent out to potential job applicants.

Despite the confusion, though, I think I can see now that there is a place for $1/hr jobs, too, since people are actually looking for these offers.