I used to write software tools used by Amazon associates inside the warehouses (fulfillment centers). I loved meeting the users and asking them 'what sucks about this?'.

A few would be too freaked out by some manager-looking-type asking them any questions. Some would say the usual stuff that we knew but couldn't help. Some would point out a few small annoyances that we would try to improve. Rarely, one would tell you things that blew your mind, like holy shit why didn't we think of that? I kept going back to try to repeat that experience.