Why does jailbreaking void warranty?

If you are modifying the shipped OS and that causes issues, since those modifications do not come from Apple, they do not provide you Support, and if something breaks, they understand it's not their fault, but yours because you are using an unsupported software (not coming from Apple or the App Store).

All details here: Unauthorized modification of iOS can cause security vulnerabilities, instability, shortened battery life, and other issu…

iOSAndroidRebel wrote:

I am just curious why jailbreaking voids warranty.

Unauthorized modification of iOS can cause security vulnerabilities, instability, shortened battery life, and other issu…

Because it is against the License Agreement one accepts when first configuring the device. Apple designed iOS devices to run its own system in order to preserve the integrity of the OS.

Jailbreaking violates the EULA for iOS and the device. It is technically a violation of the DMCA, though the courts have decided not to enforce that.

If you installed unauthorized software, modified iOS or reverse engineered the iPhone in any way; yes.

iOSAndroidRebel wrote:

Does buying iPhones on Amazon void warranty?

No.

It does not as long as the device is provided by Apple.

If it is not, and a third party vendor is selling it, you will need to contact him first and make sure they are selling it legally and first hand (like in Europe, The Phone House).

If the product is new, no seal has been broken and the box has not been opened it is OK to buy it.

If it's not and it does not come from Apple, see the status of the device at https://checkcoverage.apple.com

No, but the warranty started when the seller bought the phone, not when you buy it from the seller. So you will most likely not get a full year warranty. And, if the phone was not sold as new, and was jailbroken or repaired by the seller or a previous owner, or if the phone was stolen, or locked to a carrier, it may be worthless to you.

Don't buy those then

It is used, so be careful. If it sounds too good to be true, it probably is.

The warranty was void on that when you bought it. That's been explained to you before.