These are some of the reasons for which I tend to prefer PDF files for eBooks rather than attachment to anyone's specific viewers (Apple or otherwise). I still have 20 year old PC's running useful software (example: A $30,000 test instrument that consists of a domain-specific card plugged into a PC running Windows 95).
In general terms, the PC world has been characterized for what I usually describe as an intense respect for the hardware and software investment made by users not to become unnecessarily (or unjustifiably) obsolete. Another example I have of this is the Adobe CS4 suite, which we purchased back in 2008 and is perfectly usable (and in use on a daily basis) 12 years later across many evolutions of the Windows hardware and software landscape.
We also have Apple products, Macs, iPads, etc. I still remember Apple pushing the reset button twice; once in transitioning to the PowerPC processors and then abandoning the platform; obsoleting all existing software in the process. Twice.
Not complaining, just a historical perspective and a difference in philosophy between two segments of the market. I never go into the Apple ecosystem assuming the solutions are going to survive the test of time. On the other hand, in the PC world, it is likely safe to assume you are in full control of when you might want to obsolete the hardware and software you purchase. From a business perspective this difference is important.