Why? My take is because drums can sound so bad, and do, most of the time. (talking live drums), that anyone who's serious about drumming, probably wants to improve the tone for their own satisfaction mainly. Plus drums are a lump of clay, there's no standard at all. It's still the Wild West when it comes to tone.
There's not many instruments that you have to acquire some pretty involved mechanical skills....just to get a pure sound out of it.
A well tuned kit doesn't happen by itself. No one except drummers and the like could possibly appreciate what goes into it.
It's an unforgiving instrument. You have to impart every last thing to the drum, right down to the very tone itself.
It's not anything like a Fender where you can strum a great chord out of a nice amp and instantly sound like a pro (not necessarily play like one)
You really can't compare them to anything else, drums are in a class by themselves in regards to the tone you get from them. All stringed, and wind instruments are basically tuned the same within each family. You can't really say that about drums. Each drum can be tuned high medium or low, with a pure fundamental or unfocused and full of o-tones, resonant or dead, etc.
Lump o' clay. Which is actually pretty cool because without even trying, for better or worse, a drummers tone is like a snowflake, unique.
That said, the way the drummer plays can TOTALLY compensate for even the worst sounding kit imaginable, and in fact should be able to make musical magic as readily with a dismal sounding kit as with a great sounding kit. Indian not arrow again.