I would have to clear off my work table, at which I stand to work, dig the sewing machine out from storage, find multiple bobbins for all the different colours of thread to sew with, could not use the table for anything else until I put it all away again.
Sewing by hand makes the task portable. I can sit comfortably in front of the tv and have hand work to do while relaxing in the evenings, take to work on while visiting, even bring it with me while on holiday so that I can relax while not feeling like a slug doing nothing. ;)
The other reason is that I just prefer how the towels look.
Here is a photo of some of the towels I have so far sewn during the trip. They still need their final press but that will wait until I'm back home.