I am CTO of a small company with products that support hardware across all platforms except Linux.
On our featured product we aim for releases every 2-4 weeks.
Testing and support are huge issues. Expanding an app's target platform range requires people, equipment, and time not just for development, but full regression QA and support. We are finding that, especially with accessory hardware like Bluetooth, things don't "just work" across the range of hardware and Apple's OS releases.
We try to support it, but it often is not in the budget.