Interestingly, the Oxford University Press still inserts a comma before the 'and' in such a list, e.g.
1. The apple, orange, and melon are good for us.
The second comma is therefore known as the 'Oxford' comma. It used to be the norm, but isn't much used in current BrE. The people who devise secretarial courses are particularly averse to it.
My own (wildly speculative) theory is that whereas the comma was once regarded as a guide to intonation and pause-length, it is now mostly seen as a semantic marker. In the example above, for instance, the pause after 'apple' is more or less the same as the pause after 'orange'; nonetheless, the second comma would be omitted by most people, on the grounds that 'and' already does the comma's job. (More's the pity, to my mind.)
Here endeth the wildly speculative theory.
MrP