And even for purely UI changes, the UI totally impacts user adoption. Eg, a 90s style grey everything form is going to feel outdated to many users and they'll associate that with the rest of the software being dated (regardless of whether or not it's true). If your goal is adoption/sales, you often have to keep changing the UI even if it's not broke with regards to functionality.
Preventive maintenance?
As in, where you take your car in every year for an oil change so it doesn't end up as one gigantic blob that gums up your entire engine or having your brake pads completely disintegrate, cleaning the lint out of a sewing machine, greasing your bike gears, ...
Preventative maintenance for the win. Just bought a 90s DeaDoo, noticed it had the original grey fuel lines. I know that those lines are notorious for breaking down and plugging fuel filters, thus killing engines. However, this SeaDoo ran perfectly as-is. I was too paranoid to just run it like that so I took it apart and sure enough, the fuel filter was all plugged up - probably would have killed the engine if I hadn't checked and just kept running it
Take care of your health, little issues turn into big ones fast and you may not even realize you're sick. Find a good doctor, go see them at least once a year.
There is a faction in the US military aviation community called "reformers" who advocate for simple, rugged aircraft designs. They decry electronics, stealth, radar, EW, missiles, and sometimes even fuel as bloat that detracts from the core elements to the fighter: speed, maneuverability, and big guns. It worked in WWII, so if it ain't broke...
Back in the 70s and 80s, these reformers predicted gloom and doom for the overly complex F-15, the same way they do today about the F-35 and F-22. It turned out however, that the F-15 is the most successful fighter of all time, having shot down over a hundred jets without being bested once.
Music’s had the same(ish) notation system since the 1600s at least, and yet throughout most varied genres (in WESTERN music) up to this day, it still has done its job pretty well.