"Are there systemic forces that point this direction,"

When you can "contribute" to the community simply by clicking a delete button, rather than actually adding new and useful information, you're bound to get this sort of situation.

StackOverflow mods are appointed to police content. The more content they remove, the more it looks like they're doing their jobs.

It's the same with Wikipedia. Deleting someone else's hard work counts as a "contribution". It shows up in your profile just like writing a new multi-page article would.

When the same credit is awarded for for destroying as for creating, the destroyers are always going to win.