Well the airlines do have Timatic as above, but that would only be helpful at check in. Anything in advance would be problematic considering visa/document requirements can change with no warning at all, and people are able to book many months in advance of travel.

Some recent examples are when Dubai suddenly required Canadians to get visas, when they weren't needed previously, without much warning. Or the opposite, where Brazil has always required visas, but this summer has a temporary visa waiver for many countries, that wasn't announced that much in advance. If someone who booked 11 months in advance had relied on what was in place at booking "because the airline told me this is all I need," then it would've been a big problem in the Dubai case if found out at the airport, or mad because they spent money they didn't need to in the Brazil case.