OK then, let's put to bed the idea that 75% of people can't open HEIF files. Microsoft offers a free extension for Windows 10,
Microsoft HEIF extension.
It's not free to make Windows 10 open the files. In order for that to work, you have to also install
another extension:
'Images that are stored in HEIF files that have the .heic file extension are compressed using the HEVC format. Such files require the HEVC Video Extensions package to be installed as well. If the HEVC Video Extensions package is not installed, the HEIF Image Extension will not be able to read or write .heic files.'
That extension costs 99 cents, presumably because of the ubiquitous licensing fees mentioned earlier in the thread. The cost per person isn't a problem, and installing the extensions isn't a problem for people who know what they need to do, but it remains a problem for ordinary users who don't know what this is about and will just be frustrated when out-of-the-box Windows fails to open the files.
One could say that's Microsoft's fault for being cheap, but the cost of licenses for the hundreds of millions of Windows 10 computers adds up.
Apple doesn't have as many newish computers out there. Also, my own personal conspiracy theory is that Apple got a steep discount on the licensing fees in exchange for providing exposure of the file format.
Aside from all that, many users need to do more with their image files than just open them in Windows. They need good third party software (and other device) support.