There are various features, which you can expect from a carrental (biluthyrning) company, and getting a driver is one of the op features. When you opt for the driver from the rent a car (hyra bil) company, you can take it to be very safe. This is also very fast when compared to getting a driver on your own. This is because if you do it on your own, it would be time consuming to verify all the details given by him. It will take even more time to check if there are any criminal records. The companies do all this and thus, all you have to do is hire the driver. They make sure that all the documents are proper before hiring him.
In addition, you cannot find a driver just for a single trip outside the company. This is possible only with the rental car (hyrbil) companies as they provide employment opportunities to many people.