From what I've read from managers of recruiters from FAANG companies is:

1) Recruiters at these companies are under a large amount of pressure to bring candidates in.

2) There is only so much time in the day

3) They feel all of their time must be spent on potential hires because of #1 and #2

4) No one likes giving bad news

I don't feel like any of these reasons excuse you from being a considerate human being. Ultimately, it happens because recruiters are never rewarded for being considerate. People who fail the interview process are treated like legal liabilities.