That was just to avoid affecting other existing uses of the command polling module.  And it makes the original 5 sec default into an uber-default that each command can override to set its own default interval.

That said, it seems that ```cylc stop --wait``` is the only other use so far.  We could change the default polling interval for that too (it ```stop``` has more varied uses than ```suite-state``` though) but strictly that would be another issue...