Background via Jon Kalb:

Notice that the rule for const placement is:

const modifies what is on its left. Unless there is nothing on its left, in which case it modifies what’s on its right.

If you consistently place const after what it modifies, the rule becomes much simpler:

const modifies what is on its left.

[…] Recently, I’ve noticed that more and more C++ programmers are starting to adopt this style. In fact, a few months ago, I learned that it had a catchy name: East const.