Adults chose to organise the way that works best for the entire family. Who cares who is paying the mortgage, as a parent your only job is to do your best for the children
My thoughts exactly.
All of these comments (when OP has clearly said that the child has never actually asked to swap rooms) about 'I pay the rent/mortgage so I get what I want' are just not what I'd expect loving parents to say. If anything, it's actually the attitude I'd expect from an immature child.
Should children really not have their needs and interests considered, just because they're too young to contribute financially to the household? Nobody would leave a hungry baby or toddler wailing for ages because 'I pay the mortgage, so they'll get fed when I say so'. You might as well give them an invoice as soon as they get a paper round for the 9 months' rent they owe you (plus interest) from before they were born.
All parents make sacrifices for their children - it's a major part of what being a parent means. This is not the same as letting them have their own way and dictate to you, but it does mean that you put them first. Would people sit at home all day watching the Horror Channel with a scared and bored toddler who wants CBeebies, just because 'I'm the one who pays the rent'?
I agree with the minority of PPs that, as an adult, the whole house tends to be based around your preferences, plus you don't have shedloads of bulky toys and a need to run around letting off steam. After bedtime, the main living areas are yours to use however you see fit.
It makes more sense if there are two parents for them to share the biggest/a bigger room, but if there's just one adult, I would think that s/he would be wise and kind enough to consider who will get the most benefit from each room.