You can download firmware updates for lenses as well as camera bodies, and with MFT there's even an open standard for interchangeable lenses/bodies across manufacturers.
One reason to put up with this crap is that you can save thousands of dollars buying nice old glass for your nice new camera. But even though the glass lasts forever, once you get 50MP sensors in cameras, old glass that was designed for the best resolution of 35mm film will limit the performance of a 50MP+ image sensor. Soon, photography will be mostly computational, and big old lenses will all be museum pieces.
I don't even want to think about whether I've kept the firmware on my Sony E-mount lenses up to date.