As someone who directs certification activities for a non-profit association (of which PADI and all the certifying agencies presumably are), I can only say that in today's world, there is always pressure on these organizations to increase revenue by whatever means possible.
The reasons are generally based on practicalities -- if you want to run a decent operation that people will see as credible, you need quality people, systems, materials, et al. That stuff costs money, obviously. Sticking with the status quo will not work, especially if there are others competing in the same market (NAUI, SSI, etc.).
Therefore we now have in many professions and pursuits, like diving, a smorgasbord of speciality qualification courses and certifications. Without this type of "creative marketing," and additional revenue derived from that, the alternative would be that the cost of basic OW certification (as some have mentioned, the "cost" of the C-card) from PADI, SSI, etc. could rise high enough to discourage many divers from pursuing the sport in the first place.
I personally don't perceive any value in "membership" to PADI (or other agency) if you're not a dive instructor. However,at the end of the day everyone is accountable for figuring out whether something they may be willing to spend money on is of any real benefit to them. Caveat emptor (buyer beware) has become a timeless expression for a very, very good reason.
Happy diving to all,
CW
). They used to have a yearly photo issue that was worthwhile, but I don't recall seeing it lately. I'm not going to renew, although I have a subsciption for the next two years. The magazine might be worthwhile if you like dive vacations to far away places. 
