Are you talking about moving $HOME/snap/ to $HOME/.snap/? I’ve also been thinking about that lately. It came up in a few different conversations before, and while there are good reasons for the current design, it’s not so clear cut anymore that it is a better design than having in .snap.
The real reason this is not “hidden” is that snap/ is not just a configuration directory. This is where the writable space for all snaps live. For them to be able to write anywhere else they need interfaces that would allow them to do so.
But then, the reason why maybe it’s okay to hide them is that maybe over time snaps will tend to use the home interface or other interfaces to put their content into better places, except for the content which is naturally suitable for a hidden directory.
So this is indeed an open topic.