Clinical background is essential in clinical studies because majority of the roles you play has something to do with human life and in order to be successful in performing the task you need clinical knowledge. As stated in the question, a statistician for example does not require biological background in analyzing or developing a code for the clinical trial but will ease it’s job if he/she can relate, that is why we have biostatician. To have understanding of functionality of the product in human will help accomplishing his job better.