Why are some things sold door-to-door?

Hi,

As a side note, there are some great door-to-door salesmen going through our area. They're young but their voices have the hoarse, broken-down quality of a floor broker. They're pro sellers, very high pressure, they seem to know all the tricks, and I wonder who trained them and what the economics of the deal are? (I suspect they're part of one of the travelling clans of sellers.)

Is that how a company decides to use door-to-door people instead of DM? Because they have to add the high-pressure effect to make a sale? Or because door-to-door salesman can't be gotten rid of as easily as a mailorder piece? I wonder how conversion ratios compare, or can you even compare them?

Thanks in advance for any and all info!

Best,

- Boyd