I think it's not that they lose their mental faculties... it's that they lived most of their lives in a world without computers (at least home computers - which only became a common occurrence in the 90's, when today's older people were already in their 50's. So they just never learned to use computers and smart phones and are completely unused to their modern UIs. Even I find it hard to use many apps on my phone! Like, how am I supposed to know that wiping carefully up and to the left is the only way to do something!!!??? So, older people may try a few things, and if it's too frustrating they just find something else to do and give up. At least that's my experience with my mom and auntie. Both of them managed only to learn how to open WhatsApp and call family, but it's always an agony when they accidentally touch something and the video disappears, or pauses, or flips so they can see only themselves or some other nonsense. And that's all they use their "smart" phones for! They just wanted an old fashion phone with a big dial buttons, plus a screen to see the person on the other side.