Wire insulation deteriorates over time. Rodents like to chew through it. Water can find it's way in through plumbing or roof leaks. Higher voltage is more likely to start a fire in these instances.
The total number of fires of electrical origin in the EU is estimated to be 273,000 per year.
According to the US National Fire Protection Assocation: Fire departments responded to an estimated average of 46,700 home fires involving electrical failure or malfunction each year in 2015–2019.
Stats aside, which do you think will cause a bigger spark, 110 or 220?https://www.europeanfiresafetyalliance.org/publications/whit...
https://www.nfpa.org/News-and-Research/Data-research-and-too...
What keeps a kid from sticking something metal into it?
UK plugs and sockets are really, really, really safe. Except to stand on.
You can try pushing with something like a screwdriver (to test for live) and it's hard to pivot the plate (feels like it needs both pins to pivot), and a non round tool snags on the plastic cover plate.
On the other end, in India I saw a power strip that would accept EU, UK, or US plugs. I took one look and refused to get close, but someone else plugged my laptop in and it worked. (everything got 240 volts, which my laptop power supply was fine with)
Safety was one significant concern. 230-240V is more likely to stop a person's heart. 220 is available in most US homes for specific cases where it is more practical.
Speaking from experience, I don't think it is uncommon for a person to have been electrically shocked at some point in their lives --- often when they were a child.