Why is it important to have a receptacle next to load centers?
Convenience
It is simply convenient to have a functional receptacle near the panel to plug in equipment. No requirement as far as I know, but trivially easy to add and very useful.
No reason that it needs to be dedicated unless it is being used for a specific appliance with high current requirements. But if it is just a convenience receptacle with nothing normally plugged into it then it can be on any circuit that itself can be shared - i.e., that rules out the kitchen countertop receptacle circuits and bathroom receptacle circuit. However, as Harper noted, there are advantages at times to having this receptacle be on a circuit all by itself, so if you can spare a circuit to do that, it is a good idea - and just the cost of an extra breaker - to put this receptacle on its own circuit.
Also keep in mind that depending on location it will likely require AFCI and/or GFCI, though if the receptacle is already in place then you normally don't need to upgrade it unless you are making changes to the circuit.