It makes sense economically since the part of the population using such services is so small and may have specific demographics that justify specific treatment just from a marketing POV.
Then you want search engines to get the whole content (okay at least before they started to summarise everything but the kitchen sink) - that will always leave a loophole.
The CMS usually allows search engines to get all content. The feature is to know human browser operators and make them pay, or know archiving/unblocking services and block them.
When previously nobody would have gone through the effort to build and maintain a custom scraper against a moving target, for some small to medium size city's newspaper, now it's just one of a myriad of 'scraper profiles' you can have a near fully automated tool create.