I think they're so widespread now largely because they were so expensive when they first started becoming common that they were used in expensive equipment, and became a way of making things look higher end.
Ballpoints or other fine-tips tend to follow the shape of the recess and it does a pretty tidy job.
Contrast that with a USB charger I picked up in an emergency, unaware it had a red led that was on constantly as long as the cord was receiving power, fucking terrible design and I've thankfully replaced it, but it didn't bother me too badly when I had to use it in my room at night. I could still sleep and everything.
So cool, but so annoying.
Don't have home electronics in your bedroom is my advice.
For example: it's hard to get through summer without a fan or air conditioner in your bedroom by me. A surprising number of those come with always on lights and it's not always clear until you plug them in.
Beyond that there's just "not everyone has the luxury of a single purpose room." Especially now, lots of people need to setup their home office in their bedroom. I have a vacuum with an always on indicator light, and the only good place to put it is a bedroom. Some people have studios and their entire apartment is their "bedroom."
All in: you're right, it's best to keep your electronics out of the bedroom, but that's not always practical and way to many things have unnecessary status lights.
It doesn't bother me at night time as the light goes on only when it is in use. But the fact that it has lights at all is bothering.
Happen once and I only noticed because the light was on and I couldn't hear the water boiling because it wasn't there anymore.
They are annoying and typically insanely bright. Also, just because something has bluetooth, does mean that a blue LED is legally required.
Probably an analog is curving a 42" screen designed to be viewed on a couch across a living room.