For some people it's to learn the new mods that have 1.5 versions that will be in 1.6. There are going to be a lot of changes even from 1.5-1.6, much less 1.4.7-1.6. Just look at all the newer stuff for MPS. Add in the new mods such as Natura, Tinker's Construct, MFR's Rednet, Extra...