Comma Placement

When there are three or more terms in a single conjunction, use a comma after each term except the last. For example:

pears, oranges, and apples

blue, purple, and gold

The only time when this rule isn't followed, is when companies choose to omit it themselves. For example:

Wiseman, Wiseman and Wiseman

Jones, Brown and Deloitte

In this case, see how the company has chosen to write it and follow their lead.