I am sure that foam fell off the ET during many if not all other
Space Shuttle launches (they couldn't stop it happening on the
last mission even after all the precautions they took), so why
didn't one of the ones before STS-107 damage a Shuttle in a
similar manner as Columbia in 2003?

Was it just the way and where the foam hit Columbia on that day
and all the other missions (excluding STS-51L for other reasons)
just got lucky?

In any event, I wish the latest mission luck and a safe return,
but boy is it time to get something a bit more modern in the
manned spacecraft department. Half a billion dollars could fund
a few good robotic planetary missions as well.