They last much longer than an aluminum prop, can be reshaped if you hit something and bend it, don't shatter if you hit something, on a higher horespower motor you can get them reworked to suit what you need pitch and cup wise etc....
Depends on what you need. Down here they are a godsend when you are driving a boat with a 250hp motor going 70mph+ in this on LOTS of lakes.
Down here you really normally only see kicker size motors without a SS prop, but that probably varies regionally as we have lots of stick ups, shallow water and even pipelines you can run over.