The thing with lenses is that they're so fragile. One inadvertent bump, and it may mean that it is no longer the same old lens, even after a repair. And a repair would take weeks, if not months, with no guarantee that it can be brought back to the previous state.
And to many of us, a glass, especially a beloved one, is too personal to be shared. It is not just a piece of metal and glass, it may also house memories. I remember vividly what glasses I used during my daughter's first stage play. For a stranger to drop that "metal and glass" beyond repair would be too "painful" and hard to accept. Dropping it myself would cause me a sleepless night or two, how much more if others would?
So, no. I may be a bit selfish, but I probably wouldn't share my glasses.