Imagine you sell digital products automated or something like that. You would have to literally shut your website down if you go somewhere on a tourist visa so you don't accidently make money.
You might think there are exceptions, but no there usually aren't.
And now imagine you actually live from a digital business you run yourself. You literally can't travel on a tourist visa.
I can't legally leave the EU, more or less, as I have no control when and where I earn money. I also wouldn't travel so far for just a month or two so this is really speaking to me :)