Markstrat - Why are shelved R&D projects completed without additional budget being allocated to them ?

The R&D department will sometimes use a part of the extra budget that has been allocated to a project to complete shelved projects that are not too far from completion.   This behavior is emphasized by two factors: (1) teams over-spending in R&D because they use estimations from on-line queries; (2) "budget required for completion" that decreases over time because of additional R&D capabilities gained by completing new projects.