I was thinking the same thing.
Back when I did get grounded (15+ years ago), grounded meant:
No TV (unless it was a show I needed to watch for school work)
No friends over
No going to friends houses
No phone calls (unless it was school related, not even grandma could call and say happy b-day)
No being outside unless it was for chores
No car for any reason at all, no exceptions
No allowance for the week. Even if I was just grounded for that night, it nixed the allowance for the week.
If the family had some sort of outing planned, the family still went on the outing, without me.
And since I'd have so much extra free time on my hands, I obviously had time to do extra chores.
Say I was grounded on Saturday, the day would go something like this:
Up at 6:00 AM.
Clean the kitchen, including using a toothpick to clean under the rim of the sink.
Clean all 4 bathrooms in the house.
9:00 AM, 30 minutes for breakfast.
Clean up the dog shit in the yard
Take out the litter box
Mow the lawn
30 minutes for lunch
Clean up the attic
wash, wax and detail the parents cars
Dust every object in the house
30 minutes for dinner
Vacuum the entire house (it was 2 stories and a finished basement)
Give the dog a bath
brush the cat
Clean the kitchen after dinner
10PM, go to bed
And if I didn't get something done, or if I halfassed something, I'd get grounded another day.
If the parents thought I purposely half assed something so they wouldn't make me do it again, I got to do it every day until it was perfect for the next 30 days.