I keep seeing this pop up on so many threads and I'm always confused why people feel quite so strongly against downstairs bathrooms.
We have one - old converted/extended 2-up, 2-down, so it is off our kitchen. I've not only got used to it, I really quite like it now. It's surprisingly handy. For example...
It's great with young DCs, you can go to the loo without being a whole floor away from them (say if you only have an upstairs bathroom)
It makes getting ready in the morning so easy. I can have the baby's milk warming and the kettle boiling etc while I start the shower. I find that saves time as compared to when I had a house with an upstairs bathroom and was trudging up and down between floors. I can see it being easier when the DCs are older, they can be eating breakfast in the kitchen while I'm ten feet away showering etc.
And the same thing in the evenings - one of us bathes DC while the other is in the kitchen starting dinner, it's quite sociable really!
Also, I spend most of my time in my house downstairs. Where the loo is. Which is all very handy, really 
Yes, once in a blue moon I wake up in the middle of the nights and think, arse, I've got to go downstairs to pee, but that's so rare. The only time it was an issue was when I was heavily pregnant, and then I just admitted defeat and had a bucket in the spare room. And tbh, the stairs were so annoying I half suspect I would have put a bucket somewhere downstairs if the bathroom had been upstairs!
Now, obviously the ideal would be some form of toilet on every floor, but not every house has room for that. So why do people hate the thought of a downstairs bathroom quite so much?