That question (as most in software design) is full of tradeoffs. People using ssh interactively want uniform short delays. That behaviour enables
You make some assumptions that while mostly true aren't always. ping a system, usually it's 100+ms away, a standard delay of up to 10ms for example wouldn't be to bad (of course I have no idea if 10ms is enough to thwart timing analysis).
timing attacks. A steady flow of encrypted traffic regardless of interactive use would be optimal from a security standpoint but a waste of bandwidth.
Again, some of us wouldn't mind wasting 1k/sec (lord knows I can't type that fast =) while managing systems.
Robert
Please do not assume all of us will sacrifice possible security gains for perceived usability (in this case both your examples aren't really so good, there are better ones, what they are is left as an excercise to the reader =). -Kurt