Dumb question about nightwear

[Botbot]

DD (14 months) has been bought one of these fleecy things.

My question is - what are they for? She sleeps in a sleeping bag, but surely she'd be too hot with this and a sleeping bag, even in the depths of winter, or too cold without the sleeping bag. Or is it for people who use sheets and blankets, and you'd just put a sheet on?

Or are they just 'loungewear' for loafing about the house in?

Anyone know?

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Link not working.

If using a sleeping bag you won't need anything fleecy under it IME. I think they are more for people who don't use sleeping bags - for children who might kick covers off.