Are there situations where one would have a fever, and it would be a good idea to fly?

If a temperature check adds minimal cost or hassle, and will catch people who shouldn't fly (for their own safety, or for others' safety), then I don't see much harm in continuing it, even if it doesn't catch everyone.

But if it adds substantial cost or hassle, or would flag people who are safe to fly, then I also hope it goes away.