Surveys allow you to dip your toe in the water and uncover why drivers would join and stay with your company. Conduct stay interviews to get deeper answers. You’ll get great ammunition for your driver marketing/advertisement and good insight on what you need to change.
Please, only ask these questions if you’re serious about change. It’s worse to ask the questions and then do nothing. If you are not committed to constant improvement, don’t ask the questions and then keep putting your head in the sand like an ostrich.