I guess I just don’t understand how allowing people to upgrade to the lower-tier Keys from tickets is such a big loss for Disney. People who purchase tickets to use during the summer have 5 days of use max before they are forced to upgrade or lose the value. So it’s not like these people are packing the parks every day of the summer. They can’t use their Keys to visit the following summer unless they purchase day tickets again or upgrade to a Key they can use during the summer. That customer also didn’t get any Key discounts on food or drinks during the summer if they didn’t upgrade until the end of their final day. And Disney now has a customer who is going to visit again which means more revenue on merchandise and food. I don’t see this as a loss for Disney at all. If anything, they’re leaving money on the table by not allowing people to upgrade.
But that's an argument for Disney to just let people in the park for free because they might spend money on something else.
Like I said above - the point of the upgrade is to help the person who bought a ticket pretend that they bought a pass instead. (The person who upgrades also loses the discounts for the days they've already spent.) If the pass was blocked out, then they're getting in for free.
People buy those low-tier passes in order to go during the low(er) periods, not during the summer.
I could certainly understand if Disney wanted to incentivize sales of those lower-tier passes by, for example, offering a minor discount during the time that those lower-tier passes are blocked out. Maybe $20/day of the length of the original ticket.
Think of it another way - pretend that a theater has a season package, but it doesn't include the marquee show (ie, Hamilton). If they let the marquee ticket holders use the entirety of their ticket cost (which would already be higher than the normal show) to pay for the season package, then they're just eating that marquee show's revenue. The whole reason that show wouldn't be included in the package is because it's the marquee show - the one that that's likely going to sell out on its own. If anything - if their experience at that marquee show is good, it helps sell the rest of the season package. Offer a discount, sure, but no business at any level is going to give that away for free.
But this is assuming people aren’t doing a cost analysis of purchasing tickets vs Keys. The cost of buying two 3-day tickets (not even 5 days) plus an Enchant Key is $100 less than an Inspire Key. I doubt a whole lot of people who are willing to spend that kind of money on ticket media would be willing to do so without having the benefits of the Inspire Key.
And most people who purchase the lower tier keys either A) Don’t want to visit during the summer or B) Would visit during the summer but can’t afford to pay for single day tickets AND a Key or single day tickets throughout the year. Not allowing people to upgrade from tickets is more likely to leave money on the table for Disney than it is for them to lose money.
If people don't want to go during the summer, they're not going to buy a ticket to go during the summer. If space is limited, any business down to a mom and pop restaurant would rather have someone who can afford it over someone who can't - they don't need to let that person eat for free.
Anyone considering what you're describing would be better off just waiting until late September or October, buy an Enchant Key, and get more visits the following September at the end of the pass (if Believe and Inspire aren't available). People do that stuff all the time.
And I'm not saying "no upgrades at all". That summer ticket should be able to upgrade to Believe or Inspire (if they're available), just not to the lower-tier Keys.
And, honestly, on the lesser side of things - it's really not fair to those of us who paid full price for an Enchant Key during the normal season to let someone have free summer days that we didn't get to have. I knew what I was buying when I bought it - they should know that as well. An Enchant Key (or an Imagine Key) shouldn't cover summer days at that price.