I like having a cycle computer with cadence.
Like you, I'm a casual rider, not really training for anything. However, I have a bad habit of pushing gears that are too big for me at a cadence of 80 rpm or lower if I don't pay attention. I don't care about the number per se, but I find that if I push too big a gear (a) my quads tire and I tend to get cramps and (b) I can't ride as far/as hard the next day.
Yes, I could just count rpms for 6 sec and multiply by 10 to get cadence, but in the moment it is easier to just glance down to see the number. I normally have cadence displayed, with time (Avocet Astrale cycle computer). I'm not big into the data on my rides, I know how much time I have, and with the cadence to help me keep discipline regarding my level of effort I'm all set. I don't really care about speed or distance, I just look at them at the end of my ride.