Whenever I go shopping, I bring two canvas bags with me and fill them. That's all I can carry, basically. And having to fill a lot of that space with heavy detergent or bulky paper towels means I either need to go on a second shopping trip (which I don't want to do), or decide what things I'm /not/ getting that week.
So sure, some people might end up weaker, but I'm still lugging some heavy bags home with me each week.
I'd liken this to the "washing machine effect" that Hans Rosling explaned in his TED talk [1]. He essentially made the case that the washing machine made a huge difference in the history of the world so parents could spend more time with their kids (among other things) instead of many hours a week just washing clothes. I would say Google Shopping Express has a similar effect for shopping trips where the time spent greatly affects the amount of things an individual can accomplish in a day.