Because to hell with UX when it comes to security. Knowing the exact length of a password absolutely makes it significantly less secure, and knowing the timing of the keystrokes doubly so.
But SUDO is the one bastion where it is absolutely essential to not offer hiding keystrokes as an obscure config option, but enable for everyone and their mother?
I guess people are a bit wary of such changes because they dumb down an established system, with more to come.
However as an Ubuntu user since 8.04, I've heard these arguments with every release. Ubuntu has always simplified some things and although sometimes controversial they were often right about UX.
I don’t think you have any idea how wrong you are.
One implies the other. You turn echo off. Then you write asterisks.
> Not for security.
Consider the case of copy and pasting parts of your terminal to build instructions or to share something like a bug report. Or screen sharing in general. You are then leaking the length of your password. This isn't necessarily disastrous for most use cases but it is a negative security attribute.
That's not how it works. Sudo turns off echo but otherwise keeps the terminal in it's normal cooked canonocal mode, meaning sudo only sees what you've entered after you hit enter. To print asteriks as you type requires putting the terminal in raw mode, which has the addition consequence of needing to implement shit like backspace yourself. Still a UX win worth doing, but it's pretty clear that skipping that and just disabling echo is an easier lazier implementation.
I still doubt the claim the scheme employed by sudo was done because it "was easier."
If you know that a password is no longer than, e.g., 10 characters, that narrows down the search domain by many, many orders of magnitude, in comparison with the case when you did not know this and you had to assume that the password could have been, e.g. 18 characters long.
If you test the possible passwords in increasing length, then knowing the length would not shorten much the search, but not knowing the length may prevent an attempt to search the password by brute force, as such an attempt would fail for longer passwords, so it is not worthwhile to do unless success is expected.
With modern hashing schemes, which require both a lot of time and a lot of memory for each tested password, even one extra character in the password can make the difference between a password that can be cracked in a useful time and one that would take too much time to crack, so knowing the length can be very important for the decision of an attacker of trying the exhaustive search approach.
Knowing the length is less important only for the users who are expected to choose easy to guess passwords, as there are much less of those than the possible random passwords.
This indeed reduces the search domain by many orders of magnitude, i.e. by more than an order of magnitude for each character that you now know that it is not used by the password.
Knowing the length of the password does not matter only in antediluvian systems, which had severe restrictions on the length of a password, so you already knew that the password is no longer than, e.g., 8 characters.
Isn't it 10%?