My first car had cruise control and I used it a lot on the open road. It was a manual car and if I tapped the brake or the clutch even slightly it would disengage. I'd typically disengage it by tapping the clutch, so as not to flash my brake lights because I wasn't necessarily slowing down.
My second car didn't have it and I didn't really miss it. That was a much sportier car that really wanted to be driven by the driver rather than a computer.
My next cars were automatics, so tapping the clutch wasn't an option. Disengaging the cruise control feels like a hassle, and I very seldom use it. I'm also not thrilled with the indicators on the dashboard - in my first car there was a light on the button to turn on cruise control (i.e. enable it, not activate it), but "cruise" only appeared on the dashboard if cruise control was active. In my current car if cruise control is enabled the light shows on the dashboard even if it's not active, which bothers me because to me the purpose of the light is a reminder that it's actually doing the driving.
It's probably easy enough to disengage cruise control, I just don't use it enough to make the effort to figure it out. The vast majority of my driving around here is on local roads where I'm often feathering the gas to adjust speed for turns, corners, hills, other traffic etc. I don't consider cruise control to be appropriate on these roads.