[jblow]

Because now your ability to install your mission-critical software is dependant upon https://whatever.io actually being up. Which it certainly won't be forever.

Or, you know, maybe someone updated the whatever.io installer to make it 'better'. But you are trying to debug some problem and you made one image last month and another one this month and you're pulling your hair out trying to figure out why they are different. Oh, it's because some text changed on some web site somewhere.

You've taken a mandatory step and put it outside your sphere of control.

[squar1sm]

Good point. I guess you could still wget the script though. It's maybe like ./configure over http? I guess even if you could do it, it's probably not culture. A Dockerfile would probably just curl sh the thing and not wget it. So the default culture probably does depend on whatever.io being up.