Excellent question, and I think the reasons range wildly. In nearly all cases, if you're designing a system that helps people publish online, "content" is a very useful and (as designers would argue) irreplaceable word. It helps you talk about the form or structure of something in contrast to its content. So much of the use of "content" begins there, and is arguably perfectly good.

But, certainly amongst engineering-heavy folks who little exposure to any liberal arts -- and who may have active disdain for them -- "content" is also used dismissively. The structure is the more important thing; the content isn't.

Those two reasons are distinct but have a lot of overlap.