There's enough adequate space.
Parents need to look for something that is foldable and light enough to carry for those times when you need to fold and hold the baby.
Having the bottom deck for the purpose of pushchairs and wheelchairs is daft. For starters we already know that some parents don't give a fuck about wheelchair users, if they did, they would fold.
Secondly what about those with mobility issues and getting up and down the stairs. Last time I went upstairs, I didn't have mobility issues. Still didn't save me going face first in the stair wall when the driver slammed on the breaks.
Who picks their pram based on public transport?
I did with all 4. Started having children when there was no wheelchair access to buses. And the final one when the spaces were introduced.
The prams were purchased to fold and lightweight to get baby, toddlers and shopping on and off buses. It's really not that hard.
Some parents are ridiculous and don't give two shits about others. They don't fold when a wheelchair, who has priority, needs the space. Leave the pushchair empty and taking up space. Block the doors when they get on even though the space is full. And the poor bastard driver has to deal with it all. Ban the lot unless they have a medical exemption.
And never mind the stupid woman tried getting the pushchair on a none accessible bus and had the balls to argue with the driver and passengers who were telling her it needed to be folded and wouldn't fit. Even more, arguing when the damn thing got stuck. And to top it all off, there was no child in the thing.