Many reasons = one is changing livery scripts in the past have been quite complex and unreliable and to make items as simple as possible and easy to future proof the less compiled the asset the better, IE one proof of this is the auto numbering that is OK in pre H4 TS12 but now not working in the post SP4 TS12. From experience most people do not use the "?" function to control items of rolling stock anyway.
Its going to hard enough putting up with the flood of emails I will get over the next 2 weeks asking for help getting them to run in a trainz version they were never released for and persons asking for pet versions with out having to fault find for all the people who for what every reason have issues running a complex script that just happens to not like there trainz install or another script on there systems than just happen to clash with mine.
In the case of the 30 class most changes are in fact mesh changes not livery changes - with the 36 and 38 class I found out that as soon as you do not offer one particular loco in a class group there is someone requesting there own person favorite.
As to the 30 class I was actual only going to release that variety that I was interested in being the changes done to the 30's by the fitters at the Cowra loco depot but these locos would be such a low demanded item and of almost of no use to any other NSWGR modeler tht I was try to be kind to all.
That being said I use the DLS as a cloud backup system for my models so to speak - in reality I am very selfish and really are only producing 3D assets that I am interested in and quite happy that if you do not want to use an item to have you down load it from the DLS in the first place. I did warn, as I have been accused of doing in the past, I was going to filling up the DLS with useless junk.
Also it not worth going to to much trouble as the number of downloads a NSWGR based items gets compared to what an North American based asset gets are staggering . Most of my NSWGR specific items on average get 100 downloads where my USA outline items get 500,000 for me its not worth putting to much effort into something that is for such a limited market anyway.
I wonder if you could use scripts to still have all those different liveries, but fewer assets, which could also make it easier to find the content in a list.
Just a thought.
