I have worked in a lot of data centers as well from the early 2000's. There are things today that are a lot better than it used to be in the past.

The biggest one is server virtualization. In the past you would either share services in a single server and separate your users by userid and filesystem location, otherwise, you would put additional hardware or a machine for a given customer or purpose. Now servers are a lot faster, capacity is getting cheaper and virtualization software is available in commodity hardware, you can provide services
with less hardware than in the past.

I think the biggest challenge is moving from legacy system to new ones. That is one reason why old machines are not moving out fast enough. As new services come by, you still have to maintain those legacy systems around. That is why you end up with computer proliferation. However, I think that this is improving being that even through emulation, you can run some of these legacy programs in commodity hardware.

The real reason why "the cloud" is attractive is because it is cheaper to pay a provider than having your staff managing those systems. I do not think that it is because of environmental reasons. Yes, data centers today can be made greener with modern facilities, but at the end, it is all about the bottom line.

I do have more computers now in my life, some of them must be recycled. :). However I tend to keep computers for a long while to my wife's chagrin.