Take a closer look at the function's description.
I missed that part at first too.

Random only gives you a series of numbers in a specific order. That means that every time you restart your game... it will use the EXACT same "random" numbers in the order they were used last game.

If you want truly random numbers you first have to make the numbers used by the random-function truly random. Thats why you have to use random_seed if you want to use random numbers.

Just try it and you'll see.