I have several different addresses, depending on who you ask. I'm sure I'm not the only one. Since I own a house, obviously I have that address (but don't live there). But since I work in another location, I stay near work, so some of my registrations are there. In addition to avoid loosing things in the gaps where I move from one location to another, I have some things registered at a P.O. box, and others at my parants'.
The reason for most of the differences are because of the different requirements of the data holder, e.g. It's the address of the property where the utility is delivered (various), it must be where your car is normally parked (insurance); it must be where you sleep at night (doctors); It can't be a P.O. box, but also can't be a different hotel every 2 weeks (DVLA), etc.
I'll admit that I am not in the majority of the population, but since they are talking about this as a way of getting 100% of the population, using a method where people show-up at different addresses is not going to help. Of course another point is that if someone does not want to vote, why insist on them being registered in the first place (or is it a BB issue?)