For an individual hole - I keep count in my head. After a round, say on the next day, I can remember maybe 80% of my shots if I played on my home course. And my memory is not very good.
Last round for instance, say hole 16, hit a decent drive probably 220 in the fairway, fatted a pitching wedge from a very wet lie about 85 yards and was left just on the lip of a greenside bunker, LW chip with front foot in the bunker and much lower than back foot about 20 yards and 20 feet past the hole, the putts? this is where my memory fails. Like I said, I have a poor memory. I'm assuming pretty much everyone can do this, most probably better than me. As such, the idea of having a counting device is a strange one to me.
For round score keeping - I use a scorecard and pencil. I don't like fussing with a smart phone during a round.
I recently bought one because, honestly, I'm a horrible golfer. My slice is bad and figured what could hurt besides my wallet. I haven't had the time this week to hit the range but I feel like my swing is feeling better. I feel like my path is better and it help with weight transfer for me. I kept un-hinging it and I figured out why finally. I thought my downswing was starting from the ground up, but in reality it wasn't. I now am starting to feel the separation of hip bump and my shoulders compared to before and it helped with that. I will see if I actually got a little better on the range this weekend and keep you updated.