Because Emacs is an OS the way it should be — an extensible system with a unified UI instead of a pile of separate and hardly interoperable applications.
The more time I spend with UNIX and hear the "UNIX philosophy" used in place of argument when someone doesn't like the feature set of some software, the more I realize that we need to move on from UNIX. We should take more ideas from things like Emacs and the Lisp machines when designing our software, and less from UNIX.
You might enjoy The UNIX-HATERS Handbook [1], published in 1994. It offers a still-relevant critical perspective on the UNIX paradigm, birthed in a context that had been exposed to alternatives.
(For some additional perspective, I don't really hate UNIX, I still recall how much of a breath of fresh air it was coming from Windows, but I think it, much like the X server, is really showing its age.)
Emacs has very few self-contained mega packages; in its own way, Emacs software is built by chaining together smaller packages. Many packages are little more than extensions to other packages.
But their interop is better. Besides Emacs packages having much greater "contact surface" (packages can augment other packages, if needed), the biggest problem with UNIX philosophy is using unstructured text as exchange medium. It leads to huge waste and proliferation of bugs, as each tool or script you use has to have its own custom (and bug-ridden) parser, and outputs its own unstructured and usually undocumented data format. This is one of those moments the history of computing took a huge step backwards. All that recent push for passing JSON around instead of plaintext? That's just rediscovering what we've lost when UNIX came along.
You don't have to use $'', you can also use literal tabs (ctrl-v to insert literals). The main difference between macOS and Linux that people notice is that macOS sed doesn't itself interpret \t (so you have to use literal tabs or $'' there).
It is, but I still use it as editor and development environment (I left out integrated on purpose). Beauty of Emacs is that it is what you need/want it to be, at least in my opinion and experience. What drove me away from Vim initially is Vimscript, which I didn't mind for years, but after I decided to learn Lisp and for that purpose jumped to Emacs for few months, after I went back to Vim I was pretty disgusted. I enjoyed Vim (I use NeoVim btw) as it is, modal editing and everything, but opening init.vim made my stomach hurt every time.
Well. org-mode has its own extensible URI system of sorts.
My email links are formatted mu4e:msgid:<message identifier>. My git links are magit:<project path>::commit@<git SHA>. Remote files are just file:/ssh:<user>@<server>:<remote path>. You could write your own for whatever you want, gmail links say (although then you could just use a plain old HTTP link).
We have message-ids, but those only let you find a message if you already know how to find a message store that contains it. Add an imap server name and user id, and you're most of the way there...
