Employers hire experienced individuals and expect them to deliver the very first minute they step into the door. The employers' reasoning is they wanted results right away that is why they are willing to pay a premium for that reason.
Some employers subject their new starters into a few hours of orientation and expect them to remember everything they have mentioned during the orientation.
The truth is, every company has their own procedures. Health and safety, quality procedures, production procedures, etc. There are thousands and thousands of pages to read to be able to fully understand them and deliver what is expected from you as the new starter. Technically, experienced individual got the technical knowledge to do their work. But, the presentation may not be the same as what is expected. Modification will double up the time to produce the final product.
No matter how experienced a new started will be, their will always be that learning curve to consider. Learning curves varies depending on experience or exposure to similar working environment in the past.
Employers should understand that new starters are like new machines, break-in is necessary. For the employee, learning the procedures and methodolgies of the company.