It's a new technology, will it be supported in 5 years time? It takes too long to make change. It's only been around for 10 years, its not proven. We can't afford the money. Who else is doing this? It's complicated. Our company doesn't like change, it's a cultural thing...
There were lots of reasons for GM to ditch the electric car, the EV1. Why Barnes and Noble didn't embrace the internet first, and why SAP and Oracle still cling to the outdated architecture and revenue models while SaaS is sweeping the world.
Always lots of reasons not to change aren't there. The resistance of the old is inbuilt, and its fatal.
Either you embrace the new now, or you repent at leisure later.