If you’re a fan of sports, the following scenario may, sadly, be a familiar one: your team or favorite player has the game wrapped up with a bow 
on it. No sooner do you breathe that sigh of relief, though, then they do something stupid and you feel victory slip away.
Even those who aren’t big sports fans may know that feeling if they run an eCommerce site. They check their analytics and find that a customer was all set to checkout, maybe they even had a hefty cart worth of products, and at the last second they turned away, taking all that profit with them (and maybe giving it to your competition).
While there could be a number of reasons for this, if you demand registration before a customer can checkout, that’s probably it.
The whole point of eCommerce is that it’s supposed to be hassle-free. Otherwise, people would just jump in their car and go the traditional route. So you need to live up to this implied promise or you’ll lose customers. Enforcing a registration requirement is not doing you any favors.
That’s not to say registration doesn’t have its advantages. Obviously, once you have a customer’s email or home address, you’re looking at some pretty big opportunities down the line. In fact, people who know how to optimize contact information can make a lot of money.
So offer incentives for people to register. For example, if they register, perhaps you’ll send them some coupons. Maybe only those who have registered are eligible for certain offers. Those who planned on shopping with you again will probably go for this. Those who were making their one and only purchase probably weren’t going to register in the first place or be enticed by any of the offers you would have sent them later on.
Once a customer has decided to purchase from you, it’s your job to ensure nothing stands between them and seeing that through. This means fast loading times, friendly copy and affordable prices. However, one surefire way to lose customers is by demanding they provide you with registration information before handing over money.
Fortunately, there is eCommerce shopping cart software out there that makes registration unnecessary. You can use options like incentives to get information from interested parties and methods like upselling to add more to your revenue. Leave checkout hassles to brick-and-mortar companies where they belong. Your competition probably already has.
Source:
http://appath.com/ecommerce-resources/customers-want-easy-checkout-without-registration/