The paradox of the self-rescuing princess babydoll t-shirt

I followed a link (maybe from Feministing?) to this t-shirt:

How cute!

It says 'self-rescuing princess' in swirly letters!
I'm not going to lie.
I like black t-shirt, I like swirly letters, and I think the princess concept is cute in certain contexts (i.e t-shirts, some ball gown styles and not much else).

I looked at the sizing (I'm a medium in case anyone wants to get it for me as a gift) and at the price.

Seems OK.

Then I saw the style/sizing option. The t-shirt style for women is 'babydoll.'

It made me think a little.

Here's this very adorable t-shirt with a great description:
"If you're reading this page, we're betting that you are that superheroine. But if you're not, we know you have one in your life. Your own personal Buffy, Lara Croft, Zoe, the wielder of The Witchblade, Xena, Kim Possible, Leela, Agent 355, Ripley, Wonder Woman, or (our favorite rolemodel for little girls) Elizabeth from The Paper Bag Princess. We could go on, but you get the idea. To paraphrase, geek girls kick butt and chew bubble gum, and we're all out of gum. "Self-Rescuing Princess" is printed in turquoise blue beneath a glittery crown / tiara on this black 100% cotton, babydoll (fitted) t-shirt."

Not only did I really appreciate the Buffy reference, I liked the variety of the list.

My problem is just with the babydoll t-shirt concept.

Why do we call t-shirts for grown women babydoll shirts?

I know this has absolutely nothing to do with the theme of the shirt, or the website that offers it for sale.

But really?

We have to go out of way to give clothing sized for women a fluffy extra-girly sounding name?

What's wrong with just calling it a shirt?