Gigabit internet, or even >100mbps internet, is burst capacity. Very few people hit gigabit speeds continuously, and those that do often hit either bandwidth caps or fair use policy limitations. It's also why ISPs can use a 10gbps fiber backbone to serve gigabit to 50-100 homes, because the probability of all of those homes capping out their bandwidth at the same time is tiny.

That's also why a lot of supposedly fast ISPs absolutely crumbled when COVID hit. A lot of people started doing video calls in the morning/afternoons, which suddenly sent latency-sensitive, bidirectional, high-bandwidth data to every corner of the network. Upload speeds collapsed, gigabit networks were struggling to hit a couple hundred mbps, and DSL providers downgraded their customers to 2005 in terms of attainable network speeds.

For that reason, I think ISPs may as well offer 10gbps as a default. Their customer base is not going to make use of that capacity anyway. Only when downloading a new game, or doing a backup, or uploading a video file somewhere, does that bandwidth become a necessity. If you remove the cap on the bandwidth side, all of that capacity will remain available for a longer period of time for all of the other people in the neighbourhood.

Some cellular providers used the same reasoning for their plans here a few years back: there were no 4G speed caps, just upload/download as fast as you can, because if you're done doing your file transfer quicker, you're clearing the airwaves for other users. Of course, you'd still pay for those hefty bandwidth caps, charging >€1 per GB per month to rake in the cash.