Allegedly, on or about 19 May 2017, Rick Stevens sent:
Just why M$ (and Google and others) decided top posting was a good idea, I have no idea--but there's a lot of M$ crud I disagree with.
Oooh, can of worms, here. But I suspect it's the easiest way of keeping prior messages so the recipient can refer to them, but first show them the newest typing, so they read that straight-away, rather than scroll through umpteen pages of never-trimmed prior messages.
It doesn't work well for Q&A posts. It's usually better to discard all but the last message, and respond bit-by-bit. If a person really needs to go back to the start of a thread, they can do that, separately.
If your mail client makes quoting and responding next to impossible, I favour discarding the entire prior message. And typing your own abbreviated questions, then answer them. The main point being to make the message easy to follow.
You see the same kind of thing in hospital records kept on paper in a binder. They just stack the latest page on the top, because the top of the binder is easy to unclick and re-attach. Putting new paper into the bottom requires a lot more work. And chances are that they don't need to refer to the ancient stuff, either.