The principle (or rule or law) of least astonishment (or surprise), often abbreviated to POLA, applies to user interface design, programming language design, and ergonomics. It states that, when two elements of an interface conflict, or are ambiguous, the behaviour should be that which will least surprise the human user or programmer at the time the conflict arises.
Now mtr might be the new cool kid in the block but some of us are either hanging out in the wrong neighborhood or just plain old. We surely deserve traceroute installed by default in our Ubuntu server alongside mtr, don’t we?
P.S. FWIW RHEL seems to take POLA a little bit further, taking into consideration even the poor guys in the village.
# ls -la `which tracert`
lrwxrwxrwx 1 root root 10 Oct 27 16:28 /bin/tracert -> traceroute