... so are fine to be worn during the day!
Two-piece "outfits" just look so uncomfortable on a newborn. Waistbands? Elastic? They have no waist! They ride up and I find babies awkward to handle in "proper clothes."
I recall ex-SIL pointed out a 'dressed' baby at a party, in jeans and trainers (2 months old) and went on and on that I'd brought mine out in PJs.
DM made similar comment today about my youngest. She's not even three weeks! What's wrong with vests and rompers until they at least have a waist?!