For all we know, he could be travelling several hours to her place, so would only be able to when it's a dire need or when he has otherwise planned to go see her. She's also 75, so her son is probably in his mid 50s, and may not be all that physically able himself.
Wouldn't a "good son" do something to overcome those obstacles? Maybe go down to Home Depot and get some guys willing to do what a 75-year old American lady won't do? (OK, that's a cheap shot. Maybe they only have a Lowes or Ace Hardware in town.)
Or maybe we get back to the discussion about how kids born after a certain date were never instilled with the notion that respect for their parents goes farther than not letting somebody else cuss them out.
I don't have enough information to begin to know what questions will reveal the big picture, let alone what the answers to the situation are in this case. Probably more than anything what I'm doing is using it as an excuse to bemoan the decline and demise of the family and the notion of neighbors as opposed to people who live next door/down the block.
stay safe.