On a DC barrel jack, you can only switch the outside contact. There’s no way to switch the center one.
Regardless, the point is that it used to be common. That it’s inconvenient today to encounter both is undisputed, but it is what it is.
Ground facing outward on a barrel plug has an advantage: if it shorts against another connector, it’s less likely to cause a short (since most plugs, if they have any exposed metal, have it as ground). Not all power supplies are floating.