Yep, it was an old rule for an old time when back-end functionality, UI functionality and presentation could all get jammed into one *SP or PHP page. While the

Yep, it was an old rule for an old time when back-end functionality, UI functionality and presentation could all get jammed into one *SP or PHP page. While the times changed the common wisdom remained. There is no reason for a component that's sole purpose is to be a component should not be self contained. It is a black box to the consumers.