According to one frustrated mother of three that recently commented on the post, it's the fault of inflexible booking engines and the accommodation provider!
"Well!!!! I am a mother of 3 kids and after trying to book accommodation for a family on line, i know NOW why parents leave their kids off the reservation!!! We have 2 kids 5, 4 and a baby and do you think i could find ANY inner city hotel that could accommodate us on line!!! We could be up graded at a high cost but again i had to ring the hotel direct to get this sorted. I could not actually do this on line...so now i know why parents tend not to enter their kids on line when trying to reserve accommodation."