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I received my first digital version of MacWorld today. I already find it inconvenient trying to read it in my home office.
If you have to use Zinio, I can understand your frustrations. I'm sure they use that to prevent non-subscribers to view it. However, I found Zinio a poor substitute for e-reading, even though it did offer publishers more latitude in style choices. If Zinio is all that e-readers offered, paper magazine would still be increasing!
I suspect the much higher cost of magazine stand issues did lead to many subscriptions. However, the fact remains that paper is a much higher cost medium, even when subsidized by ads. Ad rates are closely tied to circulation numbers, so as those came down, so did the ad rates, which led to smaller editions, which meant less coverage, which led to lower purchases, which...
Even for those with questions, there are literally hundreds of faster ways to get answers... without waiting for months and hoping your question even gets published. For detailed help and even instruction on particular apps or hardware, there are very well written and current books. Many come in both paper and digital versions with links to files and videos. Of course, most have digital versions and a web site for errata and corrections.
I still haunt brick & mortar book stores (both new and used), but not so much for up-to-date reference info. By the way, TidBITS.com publishes an extensive number of titles that should be of use to anyone who has questions from general to specific. They often have bundle sales that make their normal $10 price even better!
Of course, updates are easy and free. 
Your choice of what hardware to buy is not what is driving paper away from magazines. BTW, I consider magazines and books as two very different media; I seldom throw away a paper book after reading it!