I mean, it's not really optional for Canadians _not_ to sign up for the list. It's the official list of electors. If you're a citizen, you're going to end up on the voter list one way or another.
There are many reasons an individual may choose to not be on the list (eg. domestic abuse situations).
Technically true, but you can register at the polling booth on the day of the election, and there's a checkbox that lets you opt out of saving your data in the database. [0]