Why compatibility with Microsoft may lead to legal problems

Microsoft sued TomTom (Microsoft sues TomTom over Linux and other patent claims) for patents like 5,579,517 and 5,758,352: "Common name space for long and short filenames". When TomTom was just using the badly designed FAT from Microsoft for compatibility with Microsoft products. TomTom (like other flash storage users) could just have used a decent flash filesystem like YAFFS. This is just another example why software patents lead to fragmenting compatibility between systems.