Sadly, a term even exists for the adoption of slower and simpler speech patterns when talking to a senior: Elderspeak. The American Psychology Association defines elderspeak as:
Adjustments in speech patterns, such as speaking more slowly or more loudly, shortening sentences or using limited or less complex vocabulary that are sometimes made by younger people when communicating with older adults.*
Younger people too often think that once we become seniors, we unilaterally and instantaneously lose our hearing and become dim-witted; therefore requiring slower and simpler speech patterns. They immediately forget that, just yesterday, we were their respected and revered professors, mentors, or grandparents.
Once someone internalizes the beliefs others hold about her, verses what she believes about herself, the effect on her can be devastating. It results in a loss of self-esteem and self-confidence and worse, the adoption of the belief that she is now somehow less mentally sharp or suffers from hearing loss. She begins to mentally shrink and draw into her world, becoming a shell of her former self.
To be honest, I find the pervasiveness of this behavior toward seniors, especially given the number of seniors in positions of visible power and influence around the world today, astonishing.