Site Designer/ Developer & site-to-site code similarity issue
As a designer/developer - with my own way of processing forms, use of snippets, css layout and most things in general (not ordinarily viewable absent a 'view source') I'm wondering the best approach to treating code that is found to be similar from site to site. That is, from one customer to the next. It's been expressed to me by some local businesses now the problems that have happened with designers who retain the rights/passwords to their sites who then later want seemingly high fees for making updates, or for entire rewrites. Therefore, they want to retain the rights to their own sites.
Does server-side code really need to be unique? Clearly client side should, at least main content blocks while surely sections like meta can be somewhat similar.
Should there be renaming of tags, variables, tables, etc, every time a new site is begun? Does it really matter?
I've heard of simple graphics being used by web designers from site to site, but shouldn't this occur when the designer retains the right and one way or another 'licenses back' the use of site to customer? And is this licensing a tactic to overcome code similarity by a single designer?
BTW - I'm not referring to 'templated' sites in any way here. Only portions of code that are found to be the same or similar to one another. Also, is it unrealistic for a customer to expect that a site be created entirely from scratch, even one considered to be custom.