The yearly cadence ensures that there's always a "this year's model" to upgrade corporations+institutions to in volume through the Apple Business Leasing program.
That's also why Apple bothers to do the silent little spec-bump releases: it gives Business Leasing corporate buyers a new SKU to use to justify staying on the upgrade treadmill for their 10k devices for another cycle (rather than holding off for even a single cycle because "it's the same SKU.")
That's also why Apple bothers to do the silent little spec-bump releases: it gives Business Leasing corporate buyers a new SKU to use to justify staying on the upgrade treadmill for their 10k devices for another cycle (rather than holding off for even a single cycle because "it's the same SKU.")