This holiday was invented to placate the growing force of labor as a voting block, like Columbus Day was meant to get Italian votes etc. But after the strikes and union building of the Great Depression that led to the power of unions in the post WWII USA—you know, what gave rise to the so-called "middle class" but was just the same old working class only now with union clout so they could counteract the power of the owners and bosses and all their wealth with the threat of strikes and walk outs and thereby gain a far wage (there was no shortage of rich folks in the 1950s and '60s, just not greedhead billions-for-my-grandchildren-isn't-enough rich folks) with which they could afford houses and cars etc.
But beginning under Reagan and his successful destruction of the unions as an explicit policy—and the rightwing propaganda that if you weren't rich it was your fault and the whole bogus "welfare queen in a Cadillac" campaign—the powers of unions became more and more diminished (and with the manufacturing jobs first moving to the South after air conditioning became common and made that region more livable with their reliable rightwing political machines and then "off shore" when even the Southern workers' non-union wages took too big a chuck out of the greedheads' gimungous profits) until today—LABOR DAY—it's mostly a hollow holiday to mark the end of summer.
But the fast food workers who walked out for two days recently demanding a wage that doesn't force them to apply for welfare and food stamps and other money from taxpayers so that their corporate bosses can live in luxury and fly private jets and own homes all over the world, hopefully are a sign that the age of labor complacency is coming to an end. Fingers crossed. (And yes there's less manufacturing jobs but people still work and any work that doesn't pay a fair wage needs to be unionized, including all those young folks working away at computers way more than forty hours a week just to enrich others.)