Often a patient will hesitate to visit the dentist because she is afraid of having to receive local anaesthetic. Nowadays if you need a cavity filled, with all the new innovations in bonding agents and composite restoration, dentists rarely have to cut deeply into a tooth to fill a cavity. In fact, with regular visits, your dentist can note any smaller pits or fissures developing and fill them preventatively so a deeper cavity never develops: no freezing required.
Alternatively there are patients who request anaesthetic in order to avoid feeling any sensations whatsoever associated with their treatment. We trust that our patients know their thresholds and would prefer you were comfortable so we can do our work while you relax and not feel a thing.