Do cavities require root canal therapy?

Depends: No not all cavities . It depends on how close to the nerve the cavities are. If the are into or extremely close then a root canal is most likely needed.

Not usually: Root canal therapy is usually necessary when the nerve of the tooth is inflammed or infected due to deep decay or sometimes if the decay is very close to the nerve and when the decay is cleaned out we get a "nerve" exposure. Most of the time this is not the case with cavities.

Not necessarily: Only of the decay gets close to or in the nerve of the tooth.