It's fun the first 2 times you do it. The buzz of a room full of expectant participants, the fun of a big roll of brown paper and sticky notes, marker pens and felt-tips. Not at all like work - more like playschool!
Then reality sets in.
This is dull, pointless work. Who cares about the minutia of how some clerk turns his computer on in the morning and uses his calendar? Do we really care about the optimal way to check voicemail? Isn't the client already paying its staff to do their work and run projects properly?
And the worst thing is trying to extract the info you need to build up your process map from people who simply don't have a clue what they're doing. Then, when you present it back and explain why you think they're being inefficient, they'll do their absolute best to pick out errors (even though they are the ones that fed you the info in the first place!) and make you look like an idiot in front of your superiors. You just can't win.
Plus, you do wonder why, as a top grad with good quals, you are spending your time documenting the work of some easy-go-lucky idiot that left school at 18, has no idea what they're doing and gets paid twice as much as you do. Just so that same idiot can then go on an ego trip and start acting like they're you're boss!