Most of my evening rides are 25-35 miles, and I'm not afraid of pushing too hard and possibly running out of steam prematurely. I can always limp in; and you don't know what you're capable of unless you push the limits. Now, longer weekend rides are another matter. For those, I rarely push as hard.
Unless they have a heart rate monitor, most people have no idea how hard they're going, and grossly overestimate how hard they're riding; i.e. they might think they're riding hard, but only doing 65% MHR.