Why is college so long in America?

Why is it that it takes so long to get a professional degree in the US?

In order to study Optometry or Medicine or Dentistry etc you need to do 4 years in college first, not even 1 or 2 years but 4 years whereas in the UK the 16-18 education is enough to prepare you for it.
People may want to start/support a family and at the same time pursue their passion but the length of study is off putting.

Gen eds.

The US is looking for mature people to be their doctors and lawyers, not a 21 year old whose frontal lobe is not yet fully developed.

It’s not THAT much longer than in Europe or Canada. In Canada, it’s 4 years too. In Europe, it’s 3 years with what would be overload in the US, but since the overwhelming majority need 4 years to get all the units required, it"s the same as in the US. If you overload in the US you can get your degree in 3 years, too. And if you have many AP/IB credits, you can get your degree in 3 years, too.

Do not assume there is a coherent answer to every question of this type. People will be happy to offer you post-hoc justifications, but that doesn’t make them right.

I would not want my doctor/dentist to have had only 1 year of formal education.

It’s a business. The more classes one is required to take, the more money the school makes.