I coach high school gymnasts and we tell them: "If you're sick (cold, flu, whatever), don't come to practice." Typical macho culture is to idealize Michael Jordan playing in the Finals(?) about to pass out from the flu.
But as coaches, we don't want half our team going down because Bob was so "brave" to come to practice when he was sick. In fact, Bob would be a shitty teammate if he showed up and ended up weakening our team. We care more about pragmatism than old-school notions of dedication at all cost.
And there's no guarantee that something that's mild for me would be the same for someone else. I sat next to a ~75yr old man at lunch today. Had I known at the time, I wouldn't have just sat there and thought, "pfft, I feel fine so I'm sure he'll be fine."