Besides, nuclear weapons are- if usable at all- a defensive weapon. The claim that Iran would attack Israel with nuclear weapons is primarily meant to suggest that they're crazy fanatics blinded by such a hatred that they would be happy to destroy themselves together with their enemy.
On the other hand, I'm not exactly sure why Iran doesn't give up all its nuclear capabilities. It would cost them nothing except pride, and would remove any excuse from the table for the US and Israel for their aggression and sanctions.
You don't need a truthful reason to have an excuse. Remember the whole Iraq WMD debacle?
Or, for that matter, Ukraine giving up its nuclear capabilities.
Exactly, even with conventional ammunitions they have shown a lot of restraint to avoid a nuclear response from Israel.
Israel doesn't have much in the way of a credible defense against Iranians advanced hypersonic missiles. Iran could create a mess in Israel by obliterating their de-salinization installations. If they were the blood thirsty fanatics propaganda paints them to be, that would be exactly what they would do, even knowing that in that case Israel wouldn't have much choice than making Tehran a giant glass parking lot.