Because that's exactly what happens on the IWLR.
At Central there are queues of people waiting exactly where the doors will open, everyone boards the few doors and clogs the vestibule while the aisles and turntables are completely empty. So when you finally lurch into Capital Square people have to shout to make people move down.
OK, yes I've seen the three queues at work (well more accurately three mobs that are filtered down into what should be a two abreast, or at least zipper queue through each door, by marshalls). In the past, in my ongoing door theme, I've said that TfNSW made a huge mistake deleting two doors from the specification of this CAF model, but some who use the trams tell me that it's OK, the trams fill anyway. This is of course counter intuitive as people don't like to get too far from a door and I still don't believe that the trams really fill to capacity. I've since had a conversation with people from Transdev who indicated to me (politely, but the undertones were there) that they were most unimpressed by TfNSW's tramcar design decisions made back in 2011 and it's not what Transdev would have chosen. In the end, TfNSW is artificially constricting capacity, as it does on buses and double deck trains, by having too few doors.
This is science that been around for generations and the ignorance of it in most current Australian transport administrations (and consultancies) is amazing. The other day I was looking at a 1935 IEA paper by FN Maclean, the chief designer of the NSW Tramways and he made this comment:
In view of the disinclination of boarding passengers to proceed into areas remote from a door of public conveyances, particularly blind-end areas, but rather to take a up a position reasonably close to a door, it is highly desirable to provide side-doors both at the ends and centre of a tramcar otherwise the difficulties in heavy loading and unloading, due to crowding and blockage of passage-ways at entrances and in obtaining even distribution throughout the length of the car, are accentuated.
Mass transit experts TfNSW are not, but hopefully a message is filtering through via the overseas inputs of the vehicle designs for CSELR and the Sydney Metro. They need to boot the CAFs off the IWLR and run the Citadis on it. Incidentally, TfNSW is making the same design mistake with the trams for Parramatta and Newcastle (and Transport Canberra has made the same mistake there). Even worse, the CAFs, even though they have end doors, have a poor bogie design that results in loss of seats and those sideways seats where people's feet block the aisle, thus reducing the effectiveness of the end doors. Buses seem to be a lost cause into the indefinite future. The result: Sydney has a fleet of public transport vehicles running around that never fill to capacity and people get left behind by vehicles that are considered "full" when they're not, which is just great at a time when there's a huge upsurge in demand.
Perpetually on a T3 to "I. P. Pavlova, přestup na Metro. Příští zastávka, Náměsti Míru"