Why do I have to go to SO/users to search on username.
Why can't I just use the 'normal' searchbox with for example my username.
user:peehaa but I have to use my id
Is this by design? And if so: Why?
Posting previous comments as an answer:
Usernames are not unique. That allows people who want to use their real names as username to do so without going through the cumbersome real-name-changing process.
Or, for that matter, allows users to chose whatever stupid nickname they want, like