I suspect it's because the instructions aren't as simple as they should be. The single-person exception is a good example; the Welsh gov. page of instructions reveal this quite starkly:
"You should only be outside of your home for very limited reasons, which include:
the need to obtain supplies and services for you or your household, for example food, medicine, and essential household maintenance. We encourage everyone to make this as infrequently as possible
to exercise, alone or with members of your household or support bubble. We encourage this to be done locally.
to access childcare and education
to access medical services
to access public services
to deposit and withdraw money from a bank or similar establishment
to provide care for or to help a vulnerable person; this includes getting food or medicines for them
to help the NHS by donating blood
for work purposes, or voluntary or charitable purposes, but only where it is not reasonably practicable to do this from home
to visit a cemetery, burial ground or garden of remembrance to pay your respects
to attend a place of worship
to attend a wedding, civil partnership or funeral if you are invited
to attend court or meet other legal obligations, or to vote
to escape a risk of illness or injury, such as for victims or people at risk of domestic abuse
to access services provided to victims of crime or domestic abuse or those at imminent risk of becoming victims
Whenever you leave home, you should try to minimise time spent outside of the home, and ensure you stay at least 2 metres away from anyone you don’t live with or are in a permitted support bubble with.
Can I form an extended household?No, you cannot form an extended household at alert level 4. The only exception to this is if you are an adult living alone or are in a household with a single responsible adult, you can form a support bubble with one other household.
For more information on what is meant by a single responsible adult, please see our guidance on
seeing people in private homes."
There are roughly fifty 'exceptions' to the rules, and without those exceptions society would stop functioning. But while I'm not defending the irresponsible selfish and thoughtless, I can see why some are having difficulties in following the regulations.
Having said that, I see that France has now stopped aircraft, shipping and the Channel Tunnel from operating. I think
Elvis had it right.