That's only relevant because you're including your whole thread (or part of it, if there's forks) in your email. As far as I know, there's no real reason for people to do this anymore. Email clients should be able to handle email threads themselves, and then the recipient can decide how they want to sort it.
If you're only replying to things that are specifically relevant to the section (what quoting was traditionally used for), then bottom-posting doesn't make sense.
If you're only replying to things that are specifically relevant to the section (what quoting was traditionally used for), then bottom-posting doesn't make sense.