It depends on the match up and where everything is at. Like sure in your top is pushed up and in no danger yeah he should help you well maybe since if you're 100% dead it would be a waste of time.
If you're karthus jg and you invade a lee alone you should die and any help from top would be a waste. But even in that example there are times where your laner can save you.
It's not black and white people play differently and games always play out differently.
Also the role of jg is map pressure that is your job so actually you do have to counter gank still. Like you actually don't have the right not to gank since then you're playing wrong. The only times where you should stop ganking is when it doesn't help or you're too behind to do it.
The majority of the time someone dies when invading it is there fault they made a bad play since it was clearly not safe to do it. Now if you are getting invaded and your laner isn't helping you then that is there fault and you probably can't gank due to being behind.
Like lot of times the mid laner should be the one helping since they lose the least for roaming.