If you don’t update your iOS would you get hack

Yes.

I always install every update because they are security and bug fixes

As pointed out above, if you leave your front door open it doesn't mean you are going to get robbed it just means it's more likely.

Not necessarily, but you would be vulnerable.

Kinda like not looking before crossing the street … we can’t say that you WILL be killed or injured … but you’re definitely more vulnerable.

Plus, there’s really no sound reason to NOT install the update; it has no “down side.”