Larry the boxes will have a code on them. This way you can pick through the lock sets and get as many keyed alike as you want. They probably have 20 different codes per store. If you really wanted to , you could hang around the store all day and wait for someone to but a set with the same code as you then follow them home.
Besides if someone already has a key that will fit your new front door lock what difference does it make if both use the same key. Less keys to have to carry, and if someone really wants to break in they will key or no key.