Not sure what you are getting at here Simon.
For me it is the right tool for the job. I run Emoncms on a DietPi VM (can’t really do that with Raspbian) so it works for me and may well work for others - I’m not advocating wholesale move, but it is an extremely stable, viable alternative to Raspbian that actually uses the same repo base (just does not include some unnecessary elements). In addition, it has some extremely handy tools for things like setting a static IP, disabling console, enabling Bluetooth etc.
It is lighter (so less power, writes etc), it has a builtin RamLog system (so none of the issues seen eleswhere with full logs) and there is tons of support from the 2 main developers (note the rapid updates in versions). I pointed out recently that one of their recent improvements had removed the end of boot banner with the IP address in it (so, so useful). Came back within 12 hours acknowledging the issue and stating it will return in next version. You do not see that sort of response with Raspbian.
Remember as well, it is not a new OS, it is simply a packaged version of Debian (which is all Raspbian is). It is often actually better as it will pick up more recent versions of some packages where the Debian/Raspbian repos are lagging.