Do not think the slogan is that bad, nor the appliance "ad men" who dreamed it up were advocating "forgetting" one had started the appliance. Rather, IMHO the fact that the "automatic" age had arrived and Mrs. Average American housewife no longer had to stand over a stove, washing machine or any other applinace and manually fiddle with them at certian times to get the job done.
Some "set and forget it" appliances that must truly have lived up to their slogans:
Fully automatic washing machines that laundered, changed water, spun dry,rinsed and so on with no input from Madame other than setting cycles/water temp. No more wringers, no more changing of water...
Launderess