The whole anatomy is different, not just the breasts. For some reason, the VM artist tends to draw women with a belly and wide hips, prominent behinds. This may have to do with pregnancy/fertility, but it may also just be their rendition of what was the beauty standard at the time.
Now compare that to your figure on the left. It's not just the breasts.
Now compare that to your figure on the left. It's not just the breasts.

