Its basically easier to have people on site for production, problems occur all the time and while you're at home, you cant go to dailies and view the work and get the feeback you need there and then, the process is huge. Also security issues are a big thing, backing up of work and so forth. Pipeline is a big thing for production to move forward and you wont have one at home.

As for the renderman comment....I think you'll find its pretty much STILL industry standard. Other renderers are used of course and it would be stupid of me not to acknowledge that fact, at Digital Domain we use VRAY, but we all want renderman.

Jay