Sorry, no I didn't mean only women push pushchairs.
And I would always give a wheelchair user precedent; as you say, they have less of a choice.
But you can't say parents CHOOSE to have kids, have big buggies, take the bus. I don't drive and even if I did, we couldn't afford to run a second car. We have a second hand Phil and Ted's that was given to us as we couldn't afford a double buggy when DS came along. It doesn't fold. I've been forced off a bus and not allowed on one due to not enough space, missing drs appointments.
It's not always about choice.
Personally I think bus companies should take both cases into consideration and come up with better space arrangements on their buses.