I'm not a Facebook/Instagram user so I don't know how they work, but is it true that they don't ask users to upload the biggest possible images/videos they have

I'm not a Facebook/Instagram user so I don't know how they work, but is it true that they don't ask users to upload the biggest possible images/videos they have? Kind of shocked as I thought they'd always want to siphon up as much information as they possibly can.