I am going to have to agree with Kasandaro here there are much easier and faster ways to make gil than picking chests. It was nothing to do with being afraid of mimics. Though it would be cool to eventually see some higher level chests at some point to make thieves tools useful again. And even if I did want to open a coffer I would just go farm the key since I have TH6 now.

And I am just going to assume Capn's comment was a joke since forbidden keys are a more logical choice even if picking was an option.