Of course, the 'dignity of labour' was a theme of English socialism since the Chartists. Communist Joe Jacobs, in his autobiography Out of the Ghetto says it was basic sense for agitators that if you wanted to be taken seriously by your workmates you would have to make sure that not only were you the most radical in the workshop, but also the most hardworking. In miner Dave Douglass' memoir The Wheel's Still in Spin he also talks about the need to prove his mettle in a team of company men, who take pride in working extra hard.
In the 1970s and 1980s, when 'speed up' and then lay-offs became a part of the employers' offensive, there were some radical leftists and anarchists who argued Lafargue's case for 'the right to be lazy', and for the secret strike of taking days off sick. For them the proper attitude at work was rather the opposite of Jacobs', one of skiving at every opportunity, and 'sabotage'. Those attitudes are alive in the 'slow' movement (whose intellectual roots are in Andre Gorz). I always thought that that was appealing to the inactive side of people, and not likely to be a call that would engage a positive change. And as Shag says, late capitalism seems to be very good at enforced idleness.
But today asserting the rights of labour against capital is not something the British Labour Party dares get caught out at, Jacobs' style, still less Lafargue-like. So it prefers the (still American-sounding, to my ears) 'hardworking families', which signifies both working class identity in opposition both to welfare 'scroungers' and parasitical toffs.