The way you've described it, charging at your home takes 8+ hours. You can do other tasks in parallel, so the effective cost to you is 6 seconds but that doesn't change how long it takes to charge your vehicle.
There are many use cases where charging at home is not an option, in which case understanding charging time becomes an important factor.
I like mathematics and engineering, which is why I like to understand basic facts to better address an issue rather than contort facts to dismiss an issue.
you phone literally knows when you're going to sleep, when on toilet, what cake did you have on your birthday. so you can ask it to tell you exact trips you took, and you can calculate when and how you can charge and for how long, from that data.