A USB floppy drive behaves almost identically to a USB hard drive-yet another SCSI block device. The cost of keeping support for them is minimal

This is very different from legacy PC floppy drive controllers which spoke a completely different protocol, which was very complex and full of footguns

Legacy floppy controllers also had various legacy features almost nobody used, like soft deletion of sectors (IBM added this in the 70s for use with primitive database systems), or attaching tape drives using the floppy interface (nowadays if you buy a brand new tape drive, the interface options are SAS or Fibre Channel)