The profile/shape of chainring teeth plays an important role in shifting performance and chain retention.
Chainring teeth that are designed for shifting will have several different profiles. Taller teeth to hold the chain and shorter teeth that enable the chain to shift off of them and onto another chainring.
Chainring teeth used on a single chainring don't have any need to shift so their profile is optimized for retaining/holding the chain rather than shifting performance. All the teeth will typically be symmetrical in shape but recent advances have resulted in variable tooth profiles. The teeth vary in width since chains have wide links and narrow links.