The idea of head cleaning is to take away those deposits before they become permanent. Meanwhile, other contaminants can be deposited on the heads. Cigarette smoke is famous for gumming things up inside the VTR, including the heads. If you use nothing but quality tapes and keep your VTR as free from dust and other contaminants as you can, you can reduce the frequency of head cleaning. You can't eliminate it altogether.
Some people take the easy-out by using a cleaning cartridge.
The strip passes through the transport and across the heads, theoretically cleaning everything. You'd be hard pressed to find a professional who would use one of these. There are a number of reasons. First, a few of the brands actually leave behind gummy deposits. Second, some are too abrasive and end up causing physical damage.