User blog comment:The Milkman/Grand Theft Auto V Review: Everything We Wanted?/@comment-2230400-20131008132955/@comment-3140952-20131012133014

They were interesting, and let's be honest, they were some of the few side activities that you could even do in vanilla IV. Like I said, I like constant activities.

That's pretty much what happened to me, if you ignore them your weekly income either drops or you don't get anything at all. I assume these missions were also put in place to make sure that you don't get a stream of constant, free money (pretty much like the properties in SA).