Savings accounts were created to enable users to hold their funds more securely, yet still maintain a near "liquid" access. 3 days is quite short: it takes me that long to move money internationally.
In practice, most people have ignored the feature, because they don't value the security that it offers enough. This isn't too surprising: look how many people hold their coins on exchanges, despite the repeated losses of customer funds experienced by exchanges over the years. Most people have a hard time factoring in the potential losses from less likely, but still possible disasters. One guy wrote a whole book on this subject, which may have been overkill, but it needed to be discussed I guess.
The proposed change should make things cognitively simpler for cryptocurrency investors: they have an expectation based on the functioning of other cryptocurrencies that they need to stake/lockup their coins to earn interest o those coins.
And as a side bonus, it will likely improve the security of user funds on Hive, by encouraging HBD holders to keep their funds in their own account and to lock their coins up for that small period of time.
RE: Proposal to make HBD interest payable only to savings accounts