Most scissors manufacturers offer a lifetime warrantee, but what lifetime?
If your scissors are going to fail they'll do it soon after you start using them. Unless the warrantee includes an infinite coverage against breakage (even if you drop them), then the lifetime warrantee is in fact about a year in length. Many manufacturers use warrantee as leverage to get you to send your scissors to them for sharpening. This means that you will not have your scissors until they are delivered back to you.
As for factory sharpening, consider the following:
The scissors manufacturer turns out 1000s of scissors of varying models each week and they are dedicated to that production. Do you honestly think that there is a factory department waiting to sharpen your scissors when they arrive especially when you consider that you are only one of 1000s of potential pairs that could arrive for sharpening at any time? It is not practical for the factory to work like that, so they contract the sharpening to independent sharpeners (just like the ones that call on your shop). Factory sharpening indeed!
See Also: On Free Sharpening