Microsoft is using Exchange to force corporations and IT professionals to move forward. There are three cases that prove that.
First, only recently did IIS get a POP3 service. Now IIS can be used as a low-end email server. Had Microsoft provided a POP3 service back when it incorporated the SMTP service in IIS, many administrators would have insisted on using IIS instead of Exchange, MAPI, OWA etc. for messaging. This would have been disastrous. The way email volume and needs involved, it is now obvious that messaging needs a robust and dedicated infrastructure, specifically designed for that purpose. Shortcuts such as the SMPT and POP3 services without the Exchange infrastructure and technologies (which are based on the SMTP service nonetheless) would have simply been inadequate. By forcing administrators to Exchange, Microsoft made clear that email needs its own infrastructure.
Second, taking it from here, surely email needs its own infrastructure, but that infrastructure should be well integrated with the rest of IT operations. Microsoft brilliantly made Active Directory a requirement for Exchange 2000 and later versions. Many organizations were reluctant of deploying AD, albeit of its superior directory services. Exchange deployments forced organizations to move forward to state-of-the-art directory services. Exchange needed them and corporations needed them as well.
Third, history is repeating itself now, with the advent of 64-bit architecture. After about ten years of living and working with 32-bit, it is time again to move forward to a faster architecture. Exchange needs it perhaps more than any other service, due to ever increasing email volumes. And what better way to move forward than to make the next Exchange version 64-bit only. Now, that should make a long awaited and necessary hardware upgrade cycle a reality. And 64-bit architecture is not only faster, it is way more secure as well.
One can only imagine what other technologies Microsoft will push upon us leveraging Exchange.
I agree with what Microsoft is doing in that respect. I am all for it. This way, Microsoft has protected corporations and administrators from shooting themselves in the foot, as, otherwise, they may have implemented inferior technologies, unwittingly sabotaging their own projects.