Which is stupid of AT&T. I get why they don't want to use the copper buried in your yard, as they want to eventually sell off the copper plant and POTS to a third party to operate like Verizon already did in a couple states.
But running fiber INTO YOUR HOUSE is stupid. You have to drill a new hole in your house, and if you have a finished basement there's no easy way to run new wire unless you happen to have conduit (which few people do)
Sane companies will put a little fiber to ethernet gateway on the side of your house at the service entrance, and repurpose the twisted pair telco wiring as gigabit ethernet.
Ethernet tops out a just under 1 gig (about 940 Mbps, I think). AT&T Fiber is future-proofing by running glass all the way to the gateway because they know that they will eventually offer speeds above 1 gig.
Google Fiber is already offering 2 gigs down/1 gig up service for $100/mo. And Comcast is advertising how they have faster internet than AT&T (which is a joke, but whatever) because they offer a 2 gig class of service now (but it's insanely expensive -- $300/mo with a 2-yr contract here -- requires a special installation, and is only available at relatively few addresses).
So AT&T knows that they'll need to eventually respond with 2 gig service too. The new type of installation I have can handle it. I think the gateway I have might even be capable of 2 gigs, not sure. (I only have 60/60 service, so none of that really matters to me personally, ha.)
As far as AT&T selling off their copper plant like Verizon did to Frontier, I don't think so. AT&T (or any large US telco, really) hasn't been keeping up those copper lines very well for a long time. Their plan is just to ditch them. They really have little value left. Pretty much everywhere now, AT&T will only allow existing POTS and low-end DSL to remain on that service. But once it's turned off, or you move from that location, it's forever turned off. They're not activating POTS service for any residential customers now.
As I walk around my neighborhood, I see all these cut copper lines dangling along the side of the telephone poles. Because when someone has AT&T Fiber installed, they cut down the copper line running from the pole to your house and replace it with a fiber cable. I suppose there are still homes in my neighborhood that are on Uverse (FTTN DSL) and are fine with it and/or don't know that FTTH is available. So their copper is still intact. And there may be a few elderly folks that still have landline POTS service with an intact copper line. But lots have been cut down.
As for using the internal copper wiring to deliver service from an external ONT to a gateway inside the house, that would be a mess in a lot of cases because there are lots of homes where that wiring has been disconnected from the external jack on the side of house so that the internal wiring can be used with VOIP (such as cableco home phone service). I think some of my wiring got removed years ago when AT&T first installed Uverse. So my point is that the installer would run into complications in a lot of cases, so it's just simpler to put in their own fresh, new fiber that's specifically intended for that service rather than trying to reuse the old copper.