@CarlT I already have a /48, from AA. That’s their default, which seems perhaps a bit extravagant to me. I’m both a home user and a very small business user; my wife has her own B&B business for which I provide support.
Perhaps AA wants to avoid the nightmare of renumbering if a customer is a business it starts one and then they take off like a rocket becoming the next Facebook. They’re perhaps more concerned about the hassle than conservation.
I would have thought that a lot of AA customers would be fine with a /60 or /56. If you gave out /64s to all home users then it would not be the end of the world, seeing as if you realised later that you needed more then there is an AA button that you can hit iirc that just gives you an additional /64 with no hassle. Perhaps /60s for home users and very small businesses who ask for something more, and /56s for those where there is any chance of future expansion, but basically give the users what they want but then yet more still, over the top, just in case.
The reason I would want a block larger than a /64 is for ACLs, would want adjacent address spaces of subnets to have a contiguous range with no holes, so being able to aggregate sub ranges into one. It just keeps the ACLs smaller. But some home users even with multiple /64s that are non-contiguous could just survive like that.
