If other communities (e.g. Debian, GNOME, KDE) can organize conferences, why wouldn't Ubuntu be able to regardless of Canonical's financial contributions.
Ubuntu Developer Summit To Be Held Online, More Frequently (OMG Ubuntu)
Posted Feb 27, 2013 18:14 UTC (Wed) by rahulsundaram (subscriber, #21946)
[Link]
All the other communities you mention are organic and supported by multiple vendors and managed by non-profit foundations. Ubuntu isn't and most of the cost of Ubuntu falls on Canonical.