Well, there's a reason for that. But first allow for a correction;
In this guide I've created, which I presume you are referencing the reason x-terminal-emulator.desktop is created, is to make x-terminal-emulator (The terminal as defined in update-alternatives) a selection to be chosen.
Second, the reason why I don't provide files up-front is because in spite my my reputation as a trusted member of this community, it would be — as the kids would say — mad sus to tell people "Hey, download this .desktop file to your root and you can trust me to not mess with your system as you use it!"
That's a recipe for not only multiple warnings, but if not moderated for randoms like you to write a "Useful" guide in this forum telling people to put random junk in their root which could be malicious.
So if you wonder why it's long-winded, inconvenient and slightly convoluted, there's your explanation.