My more cynical take on this is that, if people could check out, easily, without some kind of approval of an oversight committee, society would be in serious trouble. The Call of the Void is strong, only denial keeps many people going. If you could die, well, anyone could.
Certainly, I can understand the concern that some impulsive child might simply scamper into a suicide booth, quarter in hand, or that people fear that the elderly would be manipulated and pushed into the choice.
Overall, though, I sometimes wonder if so many of the people against suicide fear that they could not stop themselves if it were available. If we can do it, they can, too.