Fonts disappearing is not a big issue that will ultimately render your page useless. If the font is gone, the look of the page is slightly affected, but the content of the page remains. It's honestly not a big deal at all.
For typical "the words matter more than how the words look" content...can someone explain to me why we care about including the font?
See here: https://news.ycombinator.com/item?id=21841011
There’s also layout issues caused when replacing a font with another font, unless the metrics are precisely duplicated. There’s a reason RedHat paid a lot of money to have Liberation Sans with the exact same metrics as Arial, Liberation Serif have the same metrics as Times New Roman, and Liberation Mono have the same metrics as Courier New.