I hear you. I’d like to think we could make this look better and less ‘broken’. I’m not sure if there’s a technical limitation on us doing so, but I’ve fed this back to the right people internally.
As much as I understand the thought process behind this, it wouldn’t really work in practice 
We’d end up in a situation where extending the authorisation expiry to 30 days would leave a lot of people stuck without access to their money in cases where it genuinely should have been reversed and available for them to use; one example would be where a merchant has declined a payment at the point of sale, despite us receiving the authorisation request and approving it on our end. It wouldn’t really be fair for us to keep a hold on this money for 30 days in this kind of scenario. Sure, they could get in touch with COps to release the hold on it, but this would drive a pretty substantial increase in the workload for COps that really could be better addressed through design to make things clearer in the first place.
When you make a payment by card, you’re providing your authorisation for the merchant to take money from your account. When this authorisation is approved on our end, we move the money into a ‘hold’ account to ring-fence it from the rest of your money, typically for 7 days as most merchants come to collect it within around 2-5 days. This makes things clearer for you, since (assuming the merchant collects within 7 days) you can’t spend the same money twice.
It’s worth bearing in mind here that as far as a merchant is concerned, they never see that we’ve ring-fenced the money in your account and deducted it from the balance you can spend, and at this point, technically no money has been taken from your account - the money you see as ‘taken’ from your perspective is really just ring-fenced within your account. From the merchant’s perspective, you pay by card and authorise the payment, and some number of days later they come to collect the money owed - it’s pretty simple on their end.
If they don’t collect the money within 7 days, the ring-fenced money is automatically released and available to spend again, but at no point yet has it actually been collected by the merchant.
You’ve still given them authorisation to debit your account, though, and presumably have the goods you paid for, so you still owe them the money; this is why they can come in and (from your perspective) take the payment a second time. In reality, they’ve only ever taken the payment once - in the meantime the money was just ring-fenced by us to stop you from spending it twice, and automatically released from this status because the merchant has collected it later than they really should have.