Actually, Apple is providing more support for Windows 32-bit PC's than Microsoft is providing!
iTunes 12.1.3 32-bit is intended to run on
XP and
Vista 32-bit machines. Microsoft has totally stopped supporting
XP.
Apple realized that iTunes 11.x did not support iDevices running iOS 9.0. Also, old 32-bit machines could not run iTunes beyond 11.x. So, rather than saying "hey Windows users, buy a new 64-bit PC", Apple came up with a new 32-bit version that supports iOS 9. Of course, this move wasn't just because they're "nice guys" ... they didn't want owners of old Windows machines to avoid buying iDevices!