Congratulations, you've discovered that number systems are all arbitrary!

However, even when things are arbitrary, we would want to design them to be intuitive.

So I'll stay over here with my metric units.

Another thing is that these number systems do eventually interact with each other and having outlandish conversation tables is annoying and needless.

So yes we have good reasons why some of them are the way they are. Kelvin is scientifically easy to use, intuitive and fits right in with complex physics equations while Fahrenheit or whatever reverse system you are proposing would not.