Starbucks grew the "expensive coffee" market, and so independents had a niche to slip into (expensive, but not Starbucks) - Blockbuster did nothing to grow the "rental movie" market, and a given market in an area is roughly limited to the number of houses in said market.

People drink less office/gas station coffee than they used to, and so can drink more Starbucks/independent coffee. The same didn't happen to the mom and pop video rental places (though the ones that survived blockbuster, usually by being in a market too small to support a Blockbuster, often outlived them (the one near me closed a few years ago finally)).