You're definitely right -- it's interesting, but it's not making me any more sympathetic, because I fail to see why the lack of insurable interest is something the premium can't account for, and they fail to provide any explanation of that.
As far as insurance gambling goes, it feels fundamentally different? In gambling, the "house" that sells you the ticket sets the rules and introduces the element of chance. In insurance, the entity selling the financial product here is in no way in control of the outcome, which is the exact opposite of gambling.
Because premiums will rise across the board, so people with an insurable interest pay premiums set for people who intend to gamble or manipulate their insurance.
By demanding an insurable interest, insurance companies keep out gamblers and frauds. It also helps strengthen the idea that insurance shouldn't be abused or manipulated for a payout.
I don't see why this is true. The insurer still knows the item and its market value. So if the insured amount is higher than the market value then it only needs to increase the premium in those cases, not for everyone else.
https://en.wikipedia.org/wiki/Insurable_interest
(I don't know if that will make you more sympathetic to the legal rule or not.)