First come first served. Don't blame the people when the system is at fault. My wife often had to use the bus rather than the car to get the children to the hospital, have you seen the price of parking the car at an NHS hospital?
What do you propose, asking the woman to leave the bus in order for a disabled person to get on - in the case of my wife then missing a NHS appointment (with all the pain that entails)? Or waking a sleeping baby who will then scream for the next 20minutes and ruin that families day due to the child not getting a nap? If it is a mum alone with a baby have you ever actually tried to wake a sleeping baby while simultaniously collapsing a pram/buggy? Babies don't stand you know..