Nothing of huge value is lost. Distributions play an important part, we shouldn't forget. They can maintain something like this for users, if so inclined.
This mostly hurts third party/ancient/naive packages that you probably, eventually, won't want to install on your distribution for other reasons.
This won't affect any packages natively provided by your distribution of choice. Think those random RPMs/DEBs you get from an external vendor -- UPS, keyboard, whatever.
They've had over a decade to see the writing on the wall, adding approximately 12 lines to their entire codebase and packaging spec. Probably a net-reduction given the NIH-syndrome of these scripts.
Instead, I've seen them make this directory, put their scripts inside, and just expect things to work out. It did, arguably by chance. The compatibility was deliberate, but support isn't forever.
For those still worried, the pain is limited to about 15 minutes of writing a unit file, testing it, and waiting for ci or builds to finish!
I expect to have to do this for older or more esoteric stuff, but I also enjoy writing unit files.