Q: Why is top-posting such a bad thing?
A: Because it messes up the order in which people normally read text.
> Q: Why is top-posting such a bad thing?
My point is that you almost never read a single message in isolation, so bottom-posting makes you re-read everything you've just read all over again. If you happened to be reading an individual e-mail from the middle of a chain, bottom-posting would be slightly more convenient (and inline-quoting would lose information). Top posting gives you reverse chronological order, prioritizing what is important, and is friendly for discussions with changing number of recipients.
As soon as you attempt to have more complex conversations, say about subtle technical issues, it falls flat on its face and inline quoting becomes far preferable.
In a way, this is a culture issue similar to the whole maker schedule vs. manager schedule discussion. A lot of management types engage primarily in shallow conversations, and so they may think relying on Outlook is fine, while being totally unaware of the damage it does to the engineering part of the organization (and possibly to themselves).
 In part this is inherent to a manager's role. For example, in many cases a manager's email may simply be the message "yes, dear direct report, you have formal permission to proceed with your plan". There's just inherently less deep thinking in a management role, when compared to engineering roles. Of course, deep thinking should occur in management as well in plenty of places, and the best managers do recognize that. But unless they come from an engineering culture, they're probably not even aware what they're missing with top posting.
Personally, I am a fan of inline-quoting, but only when I know I'm talking 1:1 or with a fixed group of people. If new people are expected to be included down the line - as is frequent with conversations that seek approval or feedback in a company - then I default to top-post to preserve the history of the conversation.
I don't know how a deep engineering conversation looks when written down, because I'm yet to see any in a work setting; whenever a problem approaches any interesting complexity, someone can't handle the complexity and calls for video or IRL meeting.
If there's a culture problem, I think the "maker" group is much smaller than the group of engineers. I personally blame webmail (GMail and others), which by virtue of popularity essentially set the rules for how e-mail is supposed to work, and more importantly than defaulting to top-posting, popular webmail clients don't handle tree structure. Inline-quoting makes sense when your discussion forms a tree, and not a stream of messages.