First and foremost, i dont beleive there is any need to reinvent the wheel, developing a chat or simple comments systems will cost you in terms of both time and money, why not use tried and tested systems? and then . . .
Well, at times its also about the clients, you will never convince them to go beyond the normal, and the normal can be easily done neJoomla! Most of these clients do not necesarily need websites, but online brochures, static pages with a few updates here and there, so until and unless Chamisa convinces them of the need of high-functionality sites and introduces the necesary measures for such (he himself doesnt understands a thing about online selling) they will just want CMS based sites, so Pambili LoJoomla!