Karl Benz invented the 'first automobile' in 1885 [0]. 29 years later, in 1914, Ford built the first mass-production factory for his autos. It initially produced 4 cars/hour, an annual rate of about 15,000. In 1915, there were 8,000 cars in all of the US. [1]
I cannot find data, but let's guess that it's 10 more years before 1% of households in the US have cars. That would have meant about 500,000 cars.
1885 - 1925 is 40 years between invention of the first gas powered auto and 1% market penetration (bearing my assumption). Where was the robotics industry in 1976, 40 years ago?
Moreover, the automobile solved one problem: Moving a human from point A to point B on a paved road. Many efforts are approaching robots as consumer products by trying to solve many very hard problems all at the same time. Perhaps robotic vacuums are the (only?) successful commercial robot because they solve a similarly discrete problem.
It is understandable that we have not yet seen the type of commercial breakthroughs that we so highly anticipate. Give it another 20 years...
[0] https://en.wikipedia.org/wiki/Car#History
[1] http://www.thejournal-news.net/opinion/commentary/here-s-loo...