Only one email address can be used per customer - this is to avoid bad data, i.e. the same customer multiple times.
This means that if you have multiple orders put through under the same email address, they will all have the same customer name.
So while you may want to use the same email address on multiple orders, you may want to assign ticket orders to different names - Lead Booker allows you to do this.
You may also want to group different bookings together, e.g. if certain orders want to be sat near each other or have similar access needs. If this is the case, then you can also use the Note field for an order.