https://blog.jeremiahgrossman.com/2006/11/browser-port-scann...
Most (non-technical) Web users also don't run their own web servers, so they aren't affected. Among technical users, the proportion with NoScript is probably not as small.
I mostly use the web for reading blogs and articles, so the loss of dynamic sites isn't troublesome, but it's certainly not for most users.
(Edit: Some numerical context I have enabled Javascript for 194 sites over the last five years, whereas I encounter several new sites daily.)
Given the long and gory history of companies releasing insecure by default devices methods like this are a legitimate entry point into a network.
Yes.
Joking aside, I will add that I've been a NoScript/FlashBlock user for quite some time (more than a decade? I honestly can't remember), and while I run into some things that are frustrating (just had to disable NoScript for a tab to order plane tickets), it is refreshingly uncommon.
Yes, you can browse with default deny to JS and Flash.