This really great mark, I have been asking this same question, because I have been seeing some wallet were some sbd or steem is under savings and I ask some of my friends on steemit about it, but no good answer, but you just explained it all

The reason to put your STEEM or SBD's into savings is that it's a great security feature (just like steempower).
In case your account gets compromised it gives you time to regain control without anyone stealing your funds straight away.

Few day back when the price of sbd move up to $2, I quickly power up, but today it has move up again, but am unlucky because am not having much sbd to power up, and looking up to the next hit

Thanks so much for sharing @exyle