Because it's heavy and long, I thought that would be self evident. Like using the long barrel, completely pointless. It's not like the M4 has a lack of options. M4 with folding or collapsable stocks are ~$400 AUD or less (full metal, electric or gas). For an urban/indoor environment there is no reason to use the long version no matter what you are using it for. Well, maybe if you are using it as a poking stick.