If I install an GFCI/AFCI on a branch and it starts tripping and I look and find that there's some iffy wiring, that seems like a problem averted.
If I install these on a branch, decide that because it's not a problem (because the old breaker never tripped) I'm just ignoring the problem.
People ignore problems all the time and aren't always caught out, but sometimes "rely on good luck" runs into bad luck and bad things happen.
If I install an GFCI/AFCI on a branch and it starts tripping and I look and find that there's some iffy wiring, that seems like a problem averted.
If I install these on a branch, decide that because it's not a problem (because the old breaker never tripped) I'm just ignoring the problem.
People ignore problems all the time and aren't always caught out, but sometimes "rely on good luck" runs into bad luck and bad things happen.