I think it is important to keep in mind that (for example) a Mac user that never uses Terminal.app or another terminal-emulation app probably has no reliance on the TTY abstraction. The abstraction is present in his operating system, but if it were absent or broken, the the user would probably not notice anything different.
I had to add the word "probably" to the above statement because I have not actually tried disabling the TTY subsystem in OS X and verifying that all the apps typically used by non-programmers continue to work normally.
Moreover, when our typical Mac user visits a web site, probably nothing goes wrong if the TTY subsystem on the web server is absent or disabled. (Of course, the administrators of the server will not be able to ssh into the server, but these days, a significant fraction of web servers are adminned using methods that do not rely on anyone's being able to ssh into the servers.)
I kind of agree with parent, though: during my more obsessive moments I do get worried / depressed that a large fraction of programmers are still reliant on software reliant on the TTY abstraction. Although I appreciate minimalist software and software ecologies consisting of many small tools (each of which does one thing well) as much as the next programmer, I would have expected that in 2015 there would be popular minimalist software ecologies not reliant on the TTY abstraction.
I will end my comment with 2 paragraphs designed to prevent nitpicking replies:
Yes, I know that Plan 9 is a minimalist software ecology not reliant on the TTY abstraction. Since on its best day, back when Bell Labs' Computer Systems Research Group ran Plan 9, Plan 9 almost certainly had fewer than 500 users, I would not call Plan 9 popular, however.
I do not dispute that the TTY abstraction remains the natural and the best tool for certain peripheral tasks, e.g., driving serial ports, which continue to have their uses, e.g., in hardware hacking because serial ports are so vastly less complex than something like USB.