Required reintegration of any improvement is a feature of free software (where it applies to copyright only) and Consortium licensed deliverables (where it also often applies to patent and even trademark).
It is thought to help control the bad copy problem in general and the self-interested fork problem in particular. Open source advocates tend to think otherwise, but they tend not to see those problems at all. Open source licenses do not require reintegration at all, while shared source often requires ceding all rights to the original vendor on very limited terms. Evidently, shared source advocates like Microsoft think these problems are very real.
Consumerium License will almost certainly have to have this clause. There may be variant conditions under which reintegration is required, which might be factionally defined. This is possible only with a parametric license.