The only reasons to register are ones that directly benefit you.
When you register, here's what you'll be able to do:

You can track your orders
    •You can tell if the order has been shipped
    •You can tell if it shipped complete or partial
    •You can tell when it shipped
    •You can tell when it was delivered and who signed for it

There will be no need to re-enter your address and shipping information
for each order.

If you are a distributor, your price will show on each page in addition to
the retail price.

You can view recent order history.

You can reorder previous orders, either complete or partial without
needing to re-enter the information.

You can view recent quotes.

You can view open invoices and credits to your account.