IT WASN’T SO long ago that if you had a family to haul hither and thither, you got a minivan. In 2000, Americans bought 1.25 million of the things. By 2007, though, that number had dropped to 800,000, and it has since dropped below half a million a year. In the era of the ultra-popular SUV and crossover, minivans account for less than 3 percent of market share, according to Kelley Blue Book.