Why is it that commercial video cassettes play at a significantly higher volume than commercial DVDs? Is there a technical difference in how the sound production is traditionally done for the two media?

Commercial video cassettes (and by this I specifically mean VHS cassettes - I can't speak to other formats) invariably have a much higher sound mix than DVDs (regular format - I can't speak for Blu-Ray or HD discs). That is to say, regardless of the VCR, DVD player or television used, there is nearly always a significant volume difference when switching between a video cassette and a DVD. This is particularly noticeable when one uses the same television for both players. When one plays a DVD after a VHS cassette, one almost always has to double or in some cases triple the volume on the TV to get the same decibels. The reverse is similar: when playing a VHS cassette after having just watched a DVD, one has to drastically reduce the volume so as to not deafen the neighbors, let alone the people sitting in the room.