– until your type hoster is not reachable and things render funny, or if you waited for the font don't render at all. (Or you host them yourself (if legal) and your clients need to download them.)

– until you use Molengo from Google's font directory and find out the dots on the lowercase 'i' character render too far to the left on iPhones and iPads. (Why‽ What kind of stupid bug is that?)

– until you find out that some linux variants are set up with ghastly font renderers and your type looks relatively shabby for those clients.