Well to center something with IE6 would require either a fixed left margin, or the use of text-align:center, firefox would require with a fixed left margin or margin:auto. the use of text-align: center would require a div tag that didnt exist at the time, so all the templates would require an update anyway even with margin:auto. using a fixed margin would just be annoying since it would need to be updated if another width change was made, and if i was away at the time there would be no one to make those changes.
I didn't say stylesheets could change the ids and classes, but if i used an id or class then eBid used then it would cause issues, and if eBid were to create a new id or class or rename an existing one then that would cause issues as well.
If you take a look at my mum's templates you would see that i do use CSS, but by using style="" and not a link to an external css file, which by the way is agenst w3c standards which is something i follow as much as possible with all html based work i do.