"More than 40 years ago, when I was trying to learn to climb, by mentor told me that the number one rule for leading is this: "The leader never falls.""
Key to that is 40 years ago. Ropes, harnesses, protection pieces, belay devices are much muuuuch better now.
when that "rule" came out people were leading on goldline or hemp rope, placing pitons and doing a hip belay. So falling was not a good option since it was far less safe. Now you have nice dynamic ropes, good trad gear, comfortable/supportive harnesses and belay devices that make catches much easier.
still, today you need to know when a fall will be ok or not. there are still "no fall" zones where you could deck, hit something, pull a less than stellar placement etc.
I still have not taken a fall on trad gear but have taken plenty on bolts, i'd like to keep it that way.