I've been working with an SEO individual that is bothered by the "extra work" registering a custom post type generates. I am not a SEO professional and make no claims here.
That being said, there are quite a few instances where the archive/single pages are at the very least not needed and or generate duplicate content. no?
Take for instance the following example. Lets say I register a CPT for FAQs. I then create a 'FAQ Page' where I query the FAQs and output - perhaps paginate etc etc... You may argue that it's nice to have a .single.php for each FAQ so the user could life a permalink to send to a friend or whatever. However, it's not NEEDED. I'm sure there are probably more complicated examples that are more irksome to an SEO professional.
i've poked around a but and I don't see and can not find a simple way to register a CPT without single/archive page(s).