You need a lot of different sinks for a lot of different purposes. All Retail Food Establishments and Wholesale Food Establishments must have an air-gapped 3-compartment sink for warewashing. A 3-compartment sink is still required even if you have a dishwasher. If the dishwasher breaks, the 3-compartment sink ensures you can still properly clean and sanitizer your dishes.
You must have a designated handwashing sink in all food prep, service, and dishwashing areas. 3-compartment sinks, prep sinks, and dump sinks cannot be used for handwashing. This ensures a handwashing sink is always available and not being used for other purposes.