For a lot of homes, that's enough to provide good-enough internet throughout the building.
The issues arise when you've got a larger building, thick walls, lots of things competing for the same frequency band, a less great router, or you need the very lowest latency.
It often isn't - it's just magic like TCP/etc that is doing its job and making it feel that way for bulk non-interactive transfers. But get those people on a Zoom call or anything real-time and it'll be painful (double pain if they've subsequently got terrible bluetooth headsets and/or accidentally use their laptop's internal mic).
Doesn't help stupid ISPs split their 2.4GHz and 5GHz bands on separate SSIDs so now devices can't switch automatically and you've either got people constantly hogging the 2.4 band or barely trying to hang onto the 5GHz one in conditions where falling back to 2.4 would be appropriate.