and hear comes another reason - you're not gonna like it - but it's a fact...
just over a year ago, we were given a talk by one of the UK MOD photographers, with a demonstration of his kit, and what he actually does etc.
Any way, his kit was all Nikon - why? some one asked.
"Simple" came the answer - "we done a side by side test in Afghanistan and found the Nikon's to be more robust, and more capable of withstanding the wide range of conditions in weather, temperature and humidity that Afghanistan offers"
"What about the white lenses? Aren't they supposed to overcome that?"
"It overcomes Nikon's marketing quite nicely
And so, on that basis, all of the UK MOD's togs are equipped with a kit that would require its own 'white van' to transport around.
As i said, you may not like it - but if the UK Military have done side by side tests and found the Canon stuff wanting in a host of situations, then why wouldn't NASA.
Space is like a war scenario - it's hardly appropriate to expect a courier to pop over/ up and pick up your kit to get repaired and returned... Once Virgin Galactic is up and running, that might be possible...