Why not to use a company's CMS or site builder reason number 1,029,095:
I just did a simple Analytics setup for a new client and her site has no include folder. So each page has individual header/footer and any other global element is individually coded.
So she had no idea that for years her contact form was going to an old email she doesn't have access to.
She's missed every lead generated. 
A penny saved is a pound lost when it comes to your online presence. 
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