Why does the UK have age limits for different things ?

We have age limits for different things we do and buy for our own safety.

The age for buying fireworks is 18 because they are dangerous and need to be in responsible hands.

The age for driving a car is 17 because the roads need to be safe.

The lowest age for joining the army for training is 16.

There can be different ages for buying video games but some can be age 18 because of their violence level.

You have to be 16 to buy a lottery ticket.

You can be 16 to have a part time job but 14 for a light job.

You can be 16 to get married with parental permission but 18 without parental permission.

To buy alcohol you have to be 18.

You can be 17 to hold a pilot licence.