Also a side switcher allows to use a 3"1/2 disk like a 3" disk...switching manually the sides (yet a decent sofware can do it).
A big advantage at the time was to get access to CP/M sofware library, as most of those were on such Disk.
Also, the Disk were fare cheaper than the exotic 3", but...few CPC users actually got such drives.
== Softwares released on 3"1/2 disk==