lets say you have a magazine, and your job is to sell issues...
Stories that are interesting to the maximum number of people sell the most issues.
With this in mind, why would you ever, ever, ever feature a turbo buick. What are you going to write about? There is realistically only one aftermarket cylinder head, one or two cranks. Most people run stock headers deep into the 10s. Not many different combinations in general. Lets see, bigger turbo, intercooler, champion heads, girdle, and so and so runs 9's or tens. That could be every story in the magazine. Anything of any real interest, like an indepth story on how to hold a 109 together for world record runs has way too much of a niche interest, and the people that have this information don't want to give it up.
There really aren't any road racing buicks either. So much for any really interesting suspension stories. No real ground breaking developments, etc.
GenIII engines have a much larger following and the aftermarket is huge. New things are being developed every day. Doing stories on them makes for more interesting reading for most people.
Actually I mostly read magazines only for very general car news type stuff. Every now and then a dyno comparison catches my eye.. but for the most part, if you are reading a magazine trying to get the latest info then you either don't have a computer, or you don't realize the cutting edge in this hobby is happening right here on these msg boards.