For me it's all about getting peoples opinions, that really helps with my custom figs.
Of course it's always great to get some praise but it's not the main reason and hasn't been for along time, that said i think anyone who posts a moc deserves praise for just being brave enough.
There's nothing worse then posting something that gets ruined by nasty comments, some people just want to rip the heart out of your creation without trying to help.
So it's always a *y* from me for showing what you have done.