You shouldn't really take 1/20 chances into account when making decisions
Those are literally the odds of getting either a crit fail or a crit success in D&D
And... you probably shouldn't be making decisions in D&D based on the chance of getting a crit fail or crit success....
Not on a small scale. But on a larger-scale discussion, you absolutely should take that into account. Say you're planning to go fight a dragon with a 5-player team. In your planning, you presumably have some idea of roughly how much damage your group can deal per round, on average.
And that average ABSOLUTELY includes the likelihood that you're going to roll one or two crit fails/successes. You'd instinctively take that into account.
A similar principle applies here. "On average I'll do a little bit of damage to my opponent's deck with my Warrior - that average amount is increased somewhat by the possibility that I hit my opponent's Warrior."
The upside is so huge here that the overall "average damage" (as it were) is probably dragged up noticeably even if the likelihood of the event is small.