If you don’t use it, then no need to disable it however, the security is HIGHER than for your physical card. Read up on it online. That is what convinced me to use Samsung Pay. Also I don’t like having to reach back for my wallet to use a physical credit card. Sometimes stuff falls out that way.
I'll stick with my good old credit card, just as easy for me. Besides, I never bother locking my phone since I don't have anything on there really that's a huge issue if the phone's lost/stolen. I never access banking stuff from there, not even email... just web browsing, FaceBook, etc.... real lightweight stuff.
Too close to the "mark of the beast" for me.