Most of the time you don't have the luxury of 8 sec to go into the menu, run to take a shot that is already happening. By that time you may be too late.

It's 4 seconds.

It takes us old guys twice as long to do everything!

Just last week I was getting a lot of hand held shots at an event, with OIS on. An assistant was following me around with the tripod and other things. All of a sudden there was the opportunity for a really nice wide angle pan with several antique cars driving by. I slammed the camera onto the quick release plate, leveled quickly and got the shot...then realized the OIS was still on. Fortunately my pan was slow enough so it was OK this time. Being able to switch the stabilizer on and off with an external switch would be a very big deal for lots of us.