From a contributer's point of view, the inability to re-license practically is often a feature, not a bug. CLAs make the worst case scenario touted by GPL advocates about non-GPL licenses practical: They can profit directly and exclusively from your work without your direct consent.
Also the ability to relicense an Apache License 2.0 work is relatively unimportant (compared to, say, the ability to relicense something under a more restrictive license like the GPL).
