I can't understand why anyone would not want to have four - as long as they can afford it.
I have four, dd (9), ds1 (7), ds2 (5), ds3 (3) and baby due October.
Yes, it is obviously more expensive, although there are some "economies of scale" to be had. You can still have a tidy house if you train the children - not easy but get's better as they get older. The three older children don't tidy up of their own accord but when told to they will usually do it without grumbling. I'm lucky my oldest is a girl as she likes being "second mum". She'll often have got breakfast laid out before I'm downstairs and likes to help in other ways. And once one wants to help the others are much more likely to.
I'm also lucky to be able to afford a cleaner once a week and an ironing lady. Yes, the washing machine is on once or twice a day but at least I don't have all the ironing. Friends who have four (and who are also equally happy about it) either use the tumble dryer a lot or buy lots of non-iron clothes.
Most difficult time was when babe was very young and needed feeding pretty much on demand, trying to get the morning school run and packed lunches made was difficult but we did get into a routine where babe was fed around 6.30am, then usual breakfast routine, school run and then home or feed babe in car again around 9.30am.
It's also difficult if I want to take them out for the day by myself, but mainly because the 3 year old isn't so well behaved yet.
Also 2 and 3 year olds are difficult no matter how many (or few) siblings there are.
But my children gain enormously from having each other. They're always playing with each other. Doing things together. Yes, they squabble sometimes but again it usually involves the youngest one.
And life is so much more interesting. I remember being bored a lot of the time with just the one child. I haven't been bored for a long time now.