They can even have a summary or introductory paragraph indexed while designing a paywall that way. What they can't have is search engines able to read the whole

They can even have a summary or introductory paragraph indexed while designing a paywall that way. What they can't have is search engines able to read the whole article and not everyone else. I think this is fair, and so do the search engines. Google calls doing otherwise "cloaking" and says they penalize the ranking of sites that do it. Perhaps they're not doing so effectively enough.