I work for a big organisation, one of the main employers in the UK 
We've recently had quite a few staff members leave and then their jobs go up for interview. The last three jobs all went to internal staff from our unit. We all knew who was going to get the job before it even went to the application stage.
I had to bring all the candidates to the right room and give them their pre interview tests etc the other day. I felt awful making polite conversation with people who had gone out of the way to prepare for a job interview when I knew damn well they weren't going to get the job. I know its for 'fairness' it has to be advertised but it's such a waste of everyones time.
I overheard my manager coaching our internal candidate in the kitchen ten minutes before she interviewed her.
AIBU to think this is a waste of time and to wonder why they have to go to interview in the first place?