It's just the next step, after making the HD and everything else inaccessible for years. Besides no one has yet confirmed that its soldered, just not accessible outside the case.
I'm not defending Apple here. I'm just explaining their priorities. I replaced the RAM and the DVD drive in my current iMac, which was really hard to do and in the process I broke a sensor.
But what I am arguing is that Apple does not care about people like me and you. We are a very small part of the population. I'm willing to bet 99% of the computer-buying population never replaces even the RAM on their computer after they buy it. Apple knows this, so they build a machine to sell these people. This is the way they operate, and have been for a long long time now. That strategy is not going to change, and it is completely clear for everyone to see. That is why it boggles my mind that everytime Apple goes a step further, people on this forum go ape. Are you blind? It happened last time when they used a proprietary cable for the HDD, now when they lock down the RAM. I'd be willing to bet if they could make the 27" iMac smaller and lighter by removing the RAM access on that they'd do it in a heartbeat.
There's a simple solution if you don't like this business model, and it's not come here and complain on a forum. Buy from a different company.