Just curious...why are babies' sizes always compared to food?

Madison💁🏼 • Retailer// Married 6 yrs// Mommy to fraternal twin girls// surprise baby on the way!
Why do all the <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">pregnancy apps</a> I use always compare babies to food (fruits and veggies)? Lol. It doesn't bother me, I just am curious as to why they don't use other objects to change it up and make it fun??