@ Kubla: Where have you been? USB has always had a square connector!
The square one is a standard type B connector (i.e. the original Type B before we got mini and micro versions).
The Type B is what should be used in devices such as printers, external HDs, Phones, Tablets etc.
With the Type A being used in the Host, i.e. PC, Laptop etc. (The original Type A being the big rectangular one, i.e. pen drive connector).
Note: Some device manufacturers do do this wrong, especially with older external 2.5 HD drives, which often use a type A in the drive, when it should be a Type B at the drive end. (Presumably done as the type B was too wide to fit in the thinner cases).
Phones and tablets have space constraints, so use the mini/micro versions of the Type B, printers have no such space constraints, so continue to use the old square type B connectors instead. The same is true for many external HD caddies, especially with 3.5 inch drives.
There is even an extended version of the original square type B for USB 3, with an extra plug on the side for the extra data connection. (That way you can still plug an older USB 2 square lead into the USB 3 socket, and just access slower).
There are also micro versions of Type A, although I've rarely seen them used, as most Hosts are large enough to still fit the original Type A, such as in a Laptop, so don't really need the smaller forms. (The micro A has square edges, rather than angled edges we see in the type B connectors).