HobbitFoot IPhones' default photo format is HEIC, something that Windows doesn't open by default.
This is not a coincidence, Apple purposefully make it painful to use anything with any of their products unless it’s one of their products
This is not an Apple thing. Android phones use HEIC by default as well. This is a good thing. HEIC uses smaller file sizes and has fewer artifacts than JPEG.
None of my 3 Android phones used HEIC by default.
Which phones and how old are they?