The reason is "vaccine hesitancy" – some people don't want the shots, including up to half of medical workers. There are a few facts that you should know before getting in line:
The products are not FDA approved. They have an Emergency Use Authorization (EUA). By law, such products cannot be mandatory, and you should have to sign a detailed informed consent before receiving it.
The products are not vaccines in the usual sense – the dictionary definition had to be changed to call them that. They are experimental biologic agents, a form of gene therapy.