Why has Canon never come up with a way of ensuring the lens cap stays permanently attached to the lens?
I really don't understand the rationale behind not having an in-built solution.
How would you like it attached? Some Krazy Glue on the threads should keep it there permanently... 
Seriously, though - I hate the idea of a 'cap keeper'. The relatively small lens cap for a P&S or camcorder dangling on a string is annoying enough - a 77mm or 82mm cap is too big to dangle, not to mention the fact that with an ultrawide lens, a dangling cap would have a good chance of being part of the picture.
What would you suggest for a design?
Being the product design engineer that I am (not)...
I don't know to be honest. But seriously, you don't find this annoying at all? If you're shooting with 1 lens all day, I can put up with it. If you're switching lenses several times over a relatively short period of time, I mean, how many times do you need to put the lens cap on and off - is it in your left front pocket, or right rear... or camera bag... I know I'm labouring the point... and you've got to ensure you're always wear clothing with a pocket of sorts in the same place???
For example, with camcorders, and point and shoot cameras, there is a lens cover of sorts in the form of a shutter (electronic or manual) at the front of the lens. I know that's a little more complex with lens filters... but surely a multi billion dollar company can find a solution that's also remotely aesthetically pleasing.
Am I missing the point here? Maybe having to worry about lens caps is really the privilege of being a DSLR owner...