I read once (can't remember where) that it's often more useful to say "thanks for waiting" than "sorry I'm late." This is especially relevant when the lateness was something you could not have foreseen or controlled.

I think the key here is asking if you really owe an apology because you did something you shouldn't have or if you're apologizing for someone/something else.

Only apologize for yourself, when warranted--not every time an inconvenience or problem arises and you're in the room. If you're not responsible for it, you shouldn't be apologizing for it.