* It doesn't take a couple of months to a year. For small businesses, it takes 5 seconds to plug in a new router from an ISP that offers dual stack IPv6. All current end user machines already support IPv6, even phones and tablets.
Sure, it might take 5s to plug it in, but it will take months to a) find that ISP, and b) get the circuit from that ISP installed, and c) get the ISP to turn up that service. (I've not managed "a" yet, but I've been through "b" and "c" too many times.)
* It doesn't require expert networking folks to implement it. IPv6 is MUCH simpler than IPv4, it's totally plug'n'play because IPv6 router advertisements handle everything. ...
It's p-n-p at the desktop, NOT THE ROUTER. Having unskilled morons screwing with your router(s) is a recipe for Bad Things Happening(tm).
And there's more work necessary than just the network. Any internal services will need to be dealt with as well. (esp. your internal DNS server(s))
* It's not risky, because IPv6 runs alongside IPv4
Famous last words from someone who hasn't done a live deployment! IPv6 hosts tend to prefer IPv6 over IPv4 where both are available. So, the second IPv6 is available -- literally within seconds of the RA -- those hosts are going to start trying to make IPv6 connections. If your new IPv6 network is not 100% perfectly operational and as fast as your IPv4 network, everything is going to go to hell quickly. All of a sudden, pages that loaded instantly take seconds to *begin* to load and take minutes to finish... because it's trying to make every connection over an IPv6 network that isn't working, then it falls back to IPv4; for every connection.
* What companies get out of it is that their customer base grows, because they become reachable by all the Pacific Rim users that are being allocated IPv6 addresses because IPv4 address space ran out for them a while back.
Actually, I've known a great many US businesses that would prefer most of Asia wasn't on the internet! (99% of their spam and network attacks come from there, while 0% of their business does.)