^^ You would be surprised.
I sense sarcasm in your post
. But simply to let you know, there have been times where people had issues. Some of them sent an email with the scan of the bill, they got a replacement. Either they sent a front or if the front panel wiring is easily removable, they send a replacement for that. Although rust/corrosion isn't really covered officially, there have been times it happened- even on cases that one will not expect. They have even sent replacement during that time too. Its not just for the cabling. If the fan- especially higher RPM fans, are spin up very slow even with full power- or they don't work one fine day- what would you do? Few of those fans are pretty good ball bearing fans- and/or better sleeve bearing that you get in the market. You paid for those fans that you got with the case as well. They're not freebies. Also- depending on the case- there have been times where people even have received something that is dented- such as mesh on the 600T's sidepanel. Many people here infact have asked for a replacement and the company did give it to them.
Don't generalize and say you don't need it if you don't have an idea. This doesn't apply only to cases that carry a premium but also with cases such as this. Just because you haven't encountered the issue or no1 posted it on this forum, doesn't mean the chances of failure is 0.01% either. Its low- but its still there. Its nothing more than a safety net to prevent the hassle. There have been times where system doesn't start because of some issue with the power on switch/header. Now you tell me, if warranty wasn't there on the case- what would you do, buy a separate cable and replace it? Some use type of front panel connectors (via separate PCB) or buttons- some of which have the plastic body have a different mounting that needs identical switch to mount on the case. What would you do- use a duct-tape? Or else would you prefer buying another case? You might- not necessarily applicable for others.
Hopefully this gives you a good idea.