There can be no doubt whatsoever that even for a certification agency they need to be financially healthy in order to survive and continue to offer the services they do. PADI is a business and as such they cannot avoid the reality of needing a business model in order to remain financially healthy. Part of that business model has to do with limiting membership to people who pay to be a member.
PADI is not the only business that does this. Subscription fees are paid for everything from professional associations for doctors and professional engineers (to name only two of many), to members who pay a BAR in order to practice law and so on and so on. This is a VERY common model among professional associations. PADI is not unique in this in the very least.
What PADI offers to members is not insignificant. As a DM you might not have profited much from it but as an instructor I have relatively often consulted PADI about my approach to teaching. Particularly when I was a new instructor and trying to develop more efficient techniques for teaching I had fairly frequent contact with them. That particular service is very responsive and the expertise they have is quite good. That's one example of several services PADI offers to members. So yes, you pay to be a member but it's not just pissing money into a black hole so someone at PADI can lay back and get rich while sleeping, which is what you seem to be suggesting. They actually have a quality vision in mind and support their members with useful services.
That's why you were paying membership fees. Does that mean that everything is perfect? No. Obviously not. All positive change comes from people who are critical of the status quo. There is, however, a line between being critical and being cynical and I think you crossed that line in your post. Cynical people do not cause positive change. Critical people do.
Obviously it won't be "worth it" for everyone to pay membership fees. If you're not working as a pro it's clearly not "worth it" to keep paying. That doesn't mean that PADI is out to squeeze its members, it just means that for you as one individual member, you weren't working enough to make it worth your while. That's fine.
Does this help put it in perspective a bit?
R..