Why do cordless routers go through batteries so quickly?

Routers spin at 20,000-30,000 RPM and draw heavily, so verified-purchase reviewers and r/Dewalt threads repeatedly warn against small packs. The recurring advice is to run nothing smaller than a 5.0Ah battery, and ideally a 6.0Ah or larger, for usable runtime. Reviewers note this is inherent to the tool category rather than a flaw in any single model.