It’s neat to think about that writers in the past used bold, italics, and underline to emphasize things in different ways.
But writers on the internet can’t use underline anymore because it’s implied to be a link to click on, more so than it’s something that’s important to call attention to. Maybe underline wasn’t ever so great or needed, and bold was good for headlines and italics for quoting someone, but did we ever need the underline? Do we even miss it? Probably not.