Me neither, however there is nothing wrong with it (after a cooling off period of course). After all, a rep is likely to get far more exposure to IR issues, experience and training in a couple of years than most junior managers.
It is quite normal in other industries for managers to have had experience as staff representatives. Is it really a bad thing?
The important thing is to have turnover. Reps can only do so much in their own time. If more people stepped forward to do their bit for shorter periods of time, more might be acieved and those who have been banging their heads against walls for many years on your behalf could take an occasional break.
Fancy having a go yourself? You could always sign a letter giving away your rights to ever move into managment if it bothers you so much.
personally, I think a two year cooling off period is perfectly reasonable.
There are some reps who might even make good managers ands one or two who should probably sit on company Boards. Now there's an interesting concept.