I think a more likely explanation is that in the majority of cases when shopping for an appliance and your choices are a $1500 one and a $2000 one, you buy the cheaper one. This forces manufacturers to compete on price, and to cut costs wherever possible to remain profitable.
Additionally, I just spent 30 seconds googling and a washer/dryer set cost $495 in 1953, which is ~$4500 in today's buying power. You can buy a cheap washer/dryer set these days for $500 on sale, which is pretty incredible. I don't know what super heavy duty high end washer/dryer you could get these days for $4500, but I bet you could find one that would last 50 years.