Quote - I think it's largely an issue of creative people being the sorts to need to seek out new challenges. 

Let's skip the creative part.... a lot (perhaps most) of the new stuff for V4 is the same old over again.

I guess the main reason is sales. While V3 products may well still sell good, since a lot of people don't use V4 yet, V4 items do sell better. The V3 market is a bit saturated, the V4 market isn't.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk