Ever try to get someone to change the way they do something that they've been doing the same way for years? Ever try to break one of your own habits? It's not easy. Not because people are intentionally contrary or obstinate, but because big parts of our brains operate on autopilot, in deep grooves of habit, and establishing new pathways is hard.
This can be a serious problem for individuals or managers who find themselves in the midst of major change efforts.