No doubt that when Mrs Beeton first penned her housekeeping anthology, household help was cheap and plentiful.
And in 1923, in my revised edition, labour-saving in the home was a new feature because "The continued shortage of domestic labour and the high wages paid have forced many mistresses to take a much larger share in the work of the house themselves." (Note that it says a 'larger share' not 'do all of it by themselves'.) It still sounds like it was generally accepted that you would at least have a maid or a housekeeper to help you.
And, the America's Housekeeping Book, circa 1941, still mentions having a housekeeper as a reasonable way to manage your household duties and have enough time to tend to your children.
Heck, even Carol Brady had a housekeeper.
So, when did it go out of vogue to have help? Was it rising costs of wages? Or not being able to have live-in help?
Just think about how much easier it would be to have an extra person to do all your housework. All though, trying to manage a lazy, idle bint because that was all the help you could afford would be less fun.
Anyway, Mrs Beeton says that it is important to know how to do all the household chores, even if you don't do them yourself. That way you will know how long everything should take and you won't overload your help or leave them idle. Plus when you get a new girl you will be able to show her how to do all the things she's required to do.
I guess the moral of the story is, even if you don't have to do it yourself, you still have to know how to do. Inactivity is no excuse for inability.