I’m not who decides, and I set these on machines I set up, but this is a shell script that gets run by (mostly) everyone who installs Discourse. It needs to be as simple as possible, and we’re sure those settings work on Rasperry Pi and Mac and whatever other nonsense people try to do? And whatever method you use to test if it’s set already works on all of those platforms? Seems hard.
I wrote discourse-setup and I find making changes to it a bit scary.
Always offering to create swap is not a bad idea. Maybe just always offer to set up 3 or 4 GB of swap? But Then how much? A rule of thumb I once knew was to have swap the same size as RAM. And right now, if you don’t create swap, your only option is to control-c out. So either we’re going to force people to create swap or add another Y/N question (that will cause me to modify my scripts that run discourse-setup 
) Oh! Or we can have it controlled by a --skip-swap switch. That seems OK to me. If you’re smart enough to know about swap then you can find the switch to skip it; we can add a note about the switch in that WARNING message.
And maybe also add a note about the --skip-connection-test when that fails.
I think if they have swap set up already, it’s safe to assume that they know what they are doing.