Attribution, which is part of each and every CC 3.0 license, might be in conflict with deep values in some cultures.
The draft libre license does not require attribution, leaving people free to decide whether to attribute or not. In academia we reference even public domain works - it is part of the culture. In other contexts it might be less important. e.g. kids in rip-mix-share activities for fun (and social construction). In those contexts we should relieve the sharers of the burden of keeping track of trees of attributions in derived/mixed works. Where Attribution does matter, we can develop tools to make it easier.
Personally I would like to see license options which don't force the requirement for attribution. In fact earlier versions of the CC had attribution as an option.
As an academic -- I will always reference my sources through attribution -- even if there is no legal requirement to do so. That said I can also see why many academics may want to ensure attribution. Either way -- I think its more important to widen the knowledge base of the intellectual commons -- and if this means a "thousand flowers" of licenses -- sobeit as long as there are reciprocal compatability clauses among all the free content licenses.