Developers want to build quality stuff that they can be proud of. Time, budgets, marketing promises, and reality have a way of interfering with that. Rare is the job where you can tell your boss "We could release this now, and I could start on the next thing, but I'm not happy with the quality and would rather rework it." and they will just say "Ok, do that. Make it good. We'll tell all of our clients that they'll just have to wait for what we promised would be ready this month. They'll just have to deal with however that impacts them and their business."

More layers = more bugs, both at the software level and the business level. And there are a lot more layers now. We're not just compiling raw ASM or C and handing it to the end-user anymore. Every couple of years we add more layers to both.