Well, since I buy things piecemeal from DDB all the time, I guess I don't really see the issue. I don't really need any more monsters, I'm perfectly capable of homebrewing them when needed. But I still buy them because it's convenient and for me it's worth it.
With any of the VTTs there are options to buy add-ons and upgrades. I don't see why this would be any different. Buy the latest mod "Attack of the Killer Vegetables!" and spend a couple extra bucks to get the map as well? Works for me. If it's a financial burden (D&D is still one of the cheaper hobbies out there) then maybe the rest of the group pitches in.
I guess I just don't see why a company selling things that people enjoy using while also being completely optional is a bad thing.