Accounting
No one outside of IT cares about technology. They care about costs. Datacenters and equipment are expensive. Think of all the capital required to build a robust network, all the money paid for support contracts and licenses, and how every 2-5 years, you're buying new switches and routers and servers.
Then, compare that to a solid per-month fee. That monthly cost looks a lot lower than the expense of owning equipment.
Anyone that has actually made an Ethernet cable knows there's a lot more going on than that, but to the CFO, CEO, presidents, etc... it's a cost center. IT costs the business significant money. Now, what can we do to make it less expensive? How about this cloud thing? Then we don't have to pay for servers anymore, right?
