This blog is highly personal, makes no attempt at being politically correct, will occasionaly offend your sensibility, and certainly does not represent the opinions of the people I work with or for.
Sorry for my late answer

Context: a lecturer sent an email on the 20th at 14:07 to invite few people to a short meeting on the 25th. Later in the evening, at 21:52 one of the invitees replied that she will be there and added "sorry for my late answer".

Here was my private reply to her...

You know [name removed], I have never understood why people write "sorry for my late answer" in their emails (given that electronic mail is a completely asynchronous communication protocol). He sent his email on the 20th at 14:07 and you replied on the 20th at 21:52, for a meeting on the 25th.

It would be like somebody sending me in September a letter to invite me to a wedding in January, and after taking few days to reply by letter to confirm that I will be there, I add "sorry for my late answer" at the end of the letter.

People who write "sorry for my late answer" in a reply to an email sent earlier during the day which had no intrinsic sense of urgency (*), are simply saying "I am the kind of internet addict who usually checks emails 65,000 times a day; but today, for some reasons, I could not and that's why I feel late about this one..."

(*) An intrinsict sense of urgency is given in a situation where you usually start work at 8am and at 10 am your boss sends an email saying "Tried to call but no answer. You didn't show up this morning. Is everything all right ?". Then, if you wait (for instance because you didn't have the choice) until 7pm to reply "Sorry for the later answer. Broke my leg (and lost my phone) yesterday and spent the day at the hospital", then yes, in this case your answer was probably a bit late...