Yes I have been asking myself the same question when I started those nodes. Because the less blocks the users have to add, the better. And it would have saved me a lot of hours banging my head against the wall ...
But then we would decide that a lot of constructs aren't possible anymore. Suppose I want to delay every message 2 seconds. When a next message would arrive within 2 seconds, then the previous message would not be send. Which is not what we want...
Or you can stop a periodic interval sending only if certain conditions are met. E.g. you want to keep resend an input message (with payload ON) every second, until an input message (with payload OFF) arrives.
So it really depends on the case whether you want to stop the current timer or not. Therefore I think it is still better to have separate "stop" nodes...
