Yeah I think shear laziness is a factor. As Adywan said about CGI R2 in ROTS looking fake. One of the reasons is that he is noticably more matt than usual. Saves alot of time not having to do complicated reflection effects... lazy.

As Bester said the real props, ships, locations and sets on TPM are beautiful. Whatever you think about the story Theed looked great.

If you want to get pissed off at this kinda thing listen to the first 1/2 hr of the commentaries for ROTS and ROTJ:SE. You have the FX guys on ROTS proudly declaring that they didn't even create a physical Clone Trooper suit for Temuera to wear. And on ROTJ (During the new Jabba dance scene) you get Lucas laughing and saying "I don't get these people that say oh the CGI looks fake... it's all fake. It always has been" (Paraphrasing). Which is of course wrong, Models and puppets are REAL, it's the scale that is the illusion.

Let's have the ST done the Peter Jackson/Christopher Nolan way. All practical unless it is ABSOLUTELY impossible. With a nice bit of digital compositing to smooth things over. I never stop being amazed by the behind the scenes videos of those two guys movies. Amazing what they can achieve in camera with simple often silent-era tricks.