I have been using Macs for more than 25 years so, I don’t use a Mac because of its integration with the iPhone, although features like AirDrop and Handoff are genuinely excellent. Similar cross-device features are becoming more common on Android as well.
Apple can’t rely on locking customers into its own ecosystem forever. While iPhone owners may be more inclined to buy a Mac, many don’t even own a laptop, and plenty use Windows PCs instead.
Better integration with Windows and even Linux wouldn’t hurt Mac sales. If anything, it could make the Mac more appealing to people who currently avoid it because of ecosystem limitations.