That may be true, but in order for them to start that browser they have to have an OS. When they go their local store and buy a random computer they're going to

That may be true, but in order for them to start that browser they have to have an OS. When they go their local store and buy a random computer they're going to get Windows or MacOS if they feel like splurging. It's a non-trivial investment to install linux or to look for a PC coming with it preinstalled, especially if it's something they don't particularly care about (since they mostly use a browser).