The internal tool at G has a strict hierarchy called "components", and fbtasks is tags alone.
This means if you want to file a bug against anything at G, you could navigate this large hierarchy and find a rough spot for the bug. Regardless of that team's documentation, tooling, bug tracking helper forms, etc you could always file a bug that would get pretty close. Then someone on that team would move it into the proper component if you got it wrong.
At FB... you go to file a bug, but you need to know which tags! If you miss the right tag, that team may never see it. All teams implement their tagging differently, and many implement almost nothing at all. This devolves to pretty much all bugs being tracked through internal group posts, because at least internal groups have names and membership lists that are easily searchable. Then teams implement bots & programs to take every post filed in a group, and auto generate a task with the right tags! And pray that they append the `donotreap` tag...
Bugs need to be filed against specific systems, and those systems need to be owned by teams. Those teams are in orgs, those orgs are in companies. I cringe whenever I see a bug tracker for a large company that is not in a hierarchy.