What do you mean not crucial?

Of course it is. Quite a few online services and applications use it to hide complexity.

For instance I am currently working on redesign of a netbank which involves introducing visual overview of your spending. Flash is perfect for that.

But for some reason because many games of mouseover event's it's is an argument for why apple shouldn't allow it?

Sorry that's not an argument, that's poor reasoning.

What I mean is that most flash games require mouseover and mousemove events to be used — or else they're completely void of interactivity — no more useful than a static image.

Most web apps, on the other hand, are fully useable without the user ever seeing any tooltip. That's what I mean by crucial. To be honest, I thought it was pretty clear already.

Speaking on behalf of users of banking websites:

Please don't make your site in Flash.

I'm not I am rendering graphs in flash.

I understand now, originally read that as meaning the whole website. If Flash stuff can reasonably be done in non-Flash, I'd always vote for that being preferable.