Why can I not create keys with gpg with a key length longer than 4096 bits long? Is this due to government laws? I know the government has attempted and still is the use of encryption.

Who's government? American laws only apply to Americans, thankyou. A 4096 bit key is massively secure, no risk of it being broken for many decades, and I'd imagine there is just no benefit in using anything longer, or rather, the computational cost of doing the encryption with any regularity would outweigh the benefits.

Probably because 2^4096 represents a number (10^1252) larger than the number of electrons in the galaxy. ( A guess on my part )
You wouldn't need to use a larger key, and so the programmers don't bother since it would just decrease speed unnecessarily. And they want to use standard key lengths for the program to be useful.

Around 1024 bits, you are relying on how long an attack would take using current technology. However, around 4096 bits (10^1252), the number of electrons needed by a computer to crack a cypher are impossible to obtain, and the number of atoms needed to store rainbow tables for example is impossible as well. Even if you only needed one electron or photon per guess.

The original DES standard was crackable by some agencies, but the 8086 in use at the time wasn't powerful enough for anything stronger. The DES standard was by design a stop gap 5 year standard, since it was known that processors would be more powerful in the near future.