Anyone who has teeth needs to brush them if they want to keep them. That includes babies, toddlers, children, adults, and older adults, even our pets need their teeth brushed. What you don't want is a toddler to brush their own teeth. The adult is the one responsible for brushing their toddler's teeth.
Children do not gain the grip strength and dexterity to brush their own teeth effectively until sometime between the ages of 4 yrs to 5yrs and even then they need direct supervision and brush training to ensure they do a good job