When we use more than one adjective, e.g.
The big, red, bouncy balloon.
The list of three adjectives {big, red, and bouncy} is a list, so by rights it should be separated by commas, with an "and" between the last two terms.
If somebody asked us to describe the balloon we would without hesitation say that it is "big, red and bouncy". Going by the rules, the correct form for the first phrase given above would be to write:
The big, red and bouncy balloon.
But we virtually never see this. In lists of adjectives and is used as the exception, whereas in lists in general, to exclude it is the exception. Is it a correct technicality to include the "and", which nobody observes, thereby making it acceptable to exclude the "and" on the basis of common usage? And to write the best English we can, should we be including the "and" in lists of adjectives?