Why does ERC20 token contract not allow burning tokens?

Just curious why in the default implementation of ERC20 transfer that OZ has, it does not allow sending tokens to the zero address, ie burning them? I know there is an extensible ERC20Burnable contract, but why create another separate contract just for this? Is there some security reason?

Because it was not in the original erc20 standard.

Does it say somewhere in the original erc20 standard no burning is allowed? I just looked at it and nowhere does it have the restriction that you can't transfer to the zero address.

You are right, nope, it was not in the standard. I think the reason these are separated is for clarity. To burn is not to transfer and to transfer is better not to burn. This is just a general good practice in solidity programming.