If you are using genie plus you can use it to scan into rides. You could use your phone/individual tickets---but everyone in your party has to scan their tickets. For us having younger kids, the magic bands are just easier because they are more accessible and I don't have to worry about pulling out anything additional.
My favorite thing about the magic bands are being able to wear them directly into the pool and charge food/drinks back to my room (if staying on property). I can leave my phone in the room and not worry about having valuables at the pool. Plus the kids get a kick out of opening the door to the room with their bands.
If we were staying off property, now that there is a charge for them--I think we would highly consider skipping them especially with the reports lately of genie plus passes being gone by mid-day for many attractions.