Ugh "snug fit" pyjamas 😡

What is with this snug fit pyjamas for babies. I'm having a really hard time finding good PJs for my baby because everything I find is super tight cause of this snug fit/slim fit fad or whatever it is. He's 7 months and wears 9 month clothes (which is pretty normal I think) I put him in a set of 12 month carter PJs and it's like making marks on his arms it's so tight. I check out their website for other styles and so many of them are snug fit. Is there a purpose for this besides trying to make babies look skinnier !?! I hate sleeping in tight clothing I wouldn't want my son to!