Reason #1 I completely understand.  But reason #2 seems overplayed.  Granted, I have scened a lot where I pay no attention to things such as, “Daddy, stop!”  In fact, it gives me great pleasure to ignore such pleas when I’m in that headspace.  However, when I’m playing with someone for the first time, I do listen to “stop” and other such verbal feedback [1].  In fact, with people new to the lifestyle, sometimes they’ll get far enough into headspace where “red” and “yellow” don’t come naturally to them, but “oh fuck, lighter please” does.  (Of course, I’d make them give a “Sir” at the end first!)

Also, if I know someone well enough to ignore cries of “ow, no, stop!” then I generally don’t need to play with safewords at all. They are nice to have in case I really badly misjudge a situation, but the better of a top you are and the better you can read your bottom [2], the less you need them.

And looking outside of myself, it’s uncommon — though I wouldn’t go so far as to say “rare” — that I witness scenes where “okay I’m done” would be ignored.  So I wonder if safewords are used more as a shield against the outside world, and perhaps for a sense of security.

[1] Unless it’s specifically negotiated that sort of forced sadomasochism is something they’re looking for.

[2] It’s a combination of the two.  You can be a world-class top, but something just isn’t clicking with the bottom, or their “no” reaction is the same as the “yes!” reaction of a sub you work with regularly, for example.