Those who don't pick up phone of known people, are the people who have too much time at their disposal. Though they pretend to be busy, they have nothing to do. A genuinely busy person will pick up the phone and tell the known caller, that he should be called at some other specific time, or he can't be of help in any particular matter. Those who don't take calls, instigate callers to keep on calling at different times, to take chances of speaking finally.
More interestingly, Indians top in this Pseudo Busy category.