But it also isn't that much of a burden. So my take on it is just do it and then it never is a problem.

What are you meant to do when you have an existing site with a brand that has inaccessible colors for the headings, buttons, links, backgrounds, text etc.? Sometimes it's not as easy as making a few colors darker/lighter, and it's a huge ask to get the client to modify their brand for this, as well as updating the styling code everywhere.