Many people are trashing carpet, or are building their homes without carpet to begin with. In this case, having a G series Kirby makes very little sense. You are not supposed to use tech drive on hard floors, so you have a bulkier vacuum for no reason.
A case can be made for pre-G series Kirbys on hardwood as they are less bulky to push around. At that point there is little need for a rug renovator unless you take the rugs outside to shampoo them. The miracle head for older Kirbys has fairly soft bristles, but is only supposed to be used with an application of floor wax first. I think the risk of scuffing a hardwood floor's finish is pretty high if you are using the miracle head dry. Engineered hardwood floors these days have very robust finishes so I think it's a case by case test. Still a manufacturer's warranty on hardwood flooring is only valid if you use their suggested cleaning products, so by using Kirby wax, you are typically voiding their warranty. If you have solid hardwood in an older house though, go for it.
Kirby's G series tile cleaner system is an absolute joke. I have tried it. No thank you.
The OP posted the felt duster "Duster-Buffer" attachment and I think that's the safest way to vacuum hard floors of any type with an upright Kirby, but it's only available for pre-G series models. Plus, you can get similar or better cleaning results with many modern day upright offerings that do not require a host of separate boxed / caddy'd attachments, and some that even have built-in soft dusting rollers on the front (such as the Shark Apex Duo-Clean)
All I am saying is that for hardwood owners, the perks of owning a Kirby an all of its accessories are greatly diminished, unless you have a substantial amount of carpet in your home or are cleaning other people's homes with it.