Of course the GP's premise assumes that most devs are web frontend types that care about the HTML. Based on modern frontend libraries, is there really any default HTML that view source would see other than enough to load up the megabytes of JS code?
Yes, consider the case of server side rendering. Or even companies like Basecamp that disavow single page applications. Or massive legacy ASP, PHP and Java web apps.
I said modern, and you replied back with legacy. Not sure if I'm being trolled, you're super sacrastic above my understanding, or what.
Tons of modern systems built from and on top of legacy. Modern != !legacy. I can also access a lot of legacy systems through modern browsers.
We run a 2 year old frontend system with React server side rendering at work.