Because if you grow, the knockers grow also, very likely

And they become very special, for they are born in abundance.

Let me define udder (what a sweet word):

At the top, there are just hints where it might be.
Forced down by the sheer weight and squidgyness, they can be found much deeper down.
Then, when you follow down, you can see them grow wider and wider, like bells.
When you find the bra, custom-made, you enjoy their wideness. There are huge fat wobbly balls lodged in them, side by side.

Then, as you hands move to let them free, you see them move. It gives you a little foretaste of how they are going to come free.
Finally, after you opened the king-size bra, they tumble down.
They move much deeper, getting flat and even wider. They've lost all firmness, due to all the fattening and sweet foods.

Now, please move. Make them jingle freely, like bells.