This is more often the case with open access journals and a lot of the time the department of the researcher or the grant funding the research will have some funds set aside to pay for this. This is becoming more common, but a lot of the more prestigious journals (where publishing is more likely to help your reputation for tenure or getting more funding) aren't open access, at least not yet. It used to be the case that any journal that required you to pay to publish something was more than likely a scam: a journal with little to no review process that would publish just about anything, meaning most people wouldn't bother reading your research if they saw it published there. Things are definitely changing, but slowly.