There's a point where your life works fine and you don't particularly need to change it or learn radically new things unless you have no other option at all. In some ways, the old actions have their own benefits. The senior goes to cash her paper check at the bank because it gets her out of the house and in front of people; she saves the money on a cell phone that she doesn't use much because she stays home more than travels at her age.
Even with computers...she doesn't feel helpless or at the mercy of technology she doesn't understand. She might even reduce her vulnerability some that way; a little knowledge can be a dangerous thing.
I can self-checkout, or at some supermarkets self-scan (using a handheld scanner), but I chose the human checkout operator. It's partly economic, the supermarket doesn't discount my shop if I do the checkout work myself, so I extract a modicum of their takings towards wages for a local person rather than have it go to shareholder profit. People here need jobs.
Also there is a difference between a rationalization for a behavior and the actual behavior. Usually the rationale is actually created afterwards. Although certainly some people must have created a deliberate policy to support employment or simply out of preference for human interaction. But my supposition was just about the check depositing.
Regardless, keeping people in menial jobs is not optimal for them or for consumers and almost certainly not a policy that will generally persist when more capable AIs are available.
"Keeping" people in menial jobs isn't the issue. When the robot takes over it's because the owner-capitalists can make more profit by cutting the proles out of the loop.
It's not the job, it's money to pay for water+food+shelter that's the issue.
If rich capitalists are happy to give up their profits to make an equal society with few menial roles then your way s works. There's no evidence that's the case and lots of evidence against it.