Could it be that printed timetables are less of a priority now that most people can access timetables online, either at home on their PC, or on the move with their mobiles?
I suspect in this case it's not less of a priority, just a lot of changes at once with presumably the 901 changes given priority (the revised 571 and 901 were available before the changes took place). Keep in mind the timetables would be outsourced to a printing company with finite capacity, and I also suspect, as others have already said or implied, that many of the changes were implemented to short time scales due to the upcoming election. Presumably such changes possibly may not be able to be implemented once Parliament finishes before the election, so in order to maximise the kudos to the government have been implemented within short time scales that may have made it hard to have the timetables out in time. Having said that, I don't see the fuss, previously timetables haven't always been available in advance of changes, sometimes due to errors in the timetables or for other reasons.
In relation to your more interesting point, that of discontinuing supply of printed timetables, whilst I certainly make great use of TramTracker and metlink.mobi to look up timetables and real time information whilst out and about, it would be fair to suggest that it is still mainly a certain demographic that knows about and feels comfortable doing things that way. There are still a lot of people who don't even have the internet or a computer let alone an internet enabled phone! To use an example, my mum (in her 60s and just retired) was asking me last week about how she can get a computer and internet at home as she isn't sure of the best way to go about it. I would think it would be rather unfair to not give public transport information to people just becuse they don't have access to a computer or mobile phone, or even if they do and don't have the internet enabled on either. Maybe in 20-40 years time when most people will have grown up with the internet and phones are as ubuiquitous amongst all ages of people as they are amongst those under 40 now, but I suspect we are some way from that tipping point yet.
Also, why your concern about printed timetables? Is it cost to the taxpayer? Environmental reasons?
Whilst I would be happy to suggest we think about why we need glossy colour timetables with 7 pages of preamble and 2 maps showing the same thing (using the recently issued 901 timetable as an example) rather than the old school A3/A4 sheet of paper with a route description, map and times as existed in the 80s, I suspect the greater ideal would be to improve cost recovery of PT by promoting greater use by more people thus also achieving greater environmental outcomes at the same time (through less car use). If widely available glossy printed timetables help achieve that by making it look attractive to people prepared to consider it as an option, then keep printing them! The small amount of environmental waste is probably far less of a problem compared to the environmental damage caused by using the car in the first place.
if a printed timetable is required, it can be printed from the Metlink website on request. This would reduce the number of out-of-date timetables in circulation...
I doubt it. People aren't going to print a new timetable from the internet every time they want to catch the bus, so I suspect there will still be plenty of out of date timetables around. In fact, it may make it worse as most people are aware they can save the PDFs generated by the Metlink site and have probably done so if they think they are going to use it regularly as it is easier to ooen a PDF from the desktop than to open your browser and navigate to the timetable. Same problem.