I see what you're getting at, but he was clearly exploiting the power imbalance that he had over vulnerable people.
For starters, a younger person would have been far less likely to call out a tradie in the first place for a very simple job like this. If they had done so, do you think the tradie would have tried to get away with £60 for it, on a 'favour' basis?
Considering that they never offered him £60 - just asked which notes he needed and he grabbed the lot. Maybe their eyesight is very poor, or they have extremely painful arthritis, so they had to trust the man to take the right money rather than being able to give it to him directly.
Most people approaching 90 are very vulnerable, and they know very well that they are. If the electrician had told them with a threatening snarl that the cost of the work - even a 2-minute job - was £1,000, or £5,000, that they had to pay him now, most of them probably would if they had the money available.
It's the same principle as when a violent man intending robbery will seek to intimidate and overpower a petite lone woman in the street but wouldn't dream of trying anything with a massive 6'4" rugby player. It's not just what people try to do, but the grounds on which they have sized up and chosen their much weaker victim before deciding to deliberately exploit that weakness.