OBJ may be standard but it does not retain program specific stuff. MAX files are not just 3D Object files they are 3D Scene files for 3D Max, just as PZ3 files are Scene files for Poser. They contain information specific to those programs that allow the content to work in those programs.

OBJ files do not contain important rigging information for either of these programs and will only load a stiff unmoveable prop or figure unless the end user knows how to re-rig the item in their particular program. It also does not contain program specific material shaders like the Poser Shader nodes which only work in Poser and a few programs that have Poser import features. 

If you see something in a format that you can not use, I reccommend you ask the uploader to share a format that you can use, but forcing all uploads to be generic OBJ will cut down on the content provided by this site. It's a bit unreasonable.

It is a miracle that curiosity survives formal education. - Albert Einstein