Why do the police have more than that? And how many times do you read about a group of cops shooting many dozens of rounds to down a perp? If I am exercising self defense with a 30 round magazine and I only need 7 or less fine, but I wouldn't like the idea of running out and needing more.
Because it says so, right in the Declaration of Independence, and in the Constitution.
"We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. And that our Standing Army of Police, which we'll only have long, long after we are dead, shall have the Right to Unlimited size magazines (which we haven't invented yet), and that They Shall have the Right to Military Grade Weaponry. But There'll be Naught for the Peasants."
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed, except when the Leaders of our great-great-great-great children feel like it. But the Standing Army of Police, which Won't be Created until the 20th Cenutry, shall have the Right to Unlimited Ammunition, and Military Grade Weaponry."
Wassamattayou? Can't you read? LOL! :)