Because a 2 year old isn't awake that long in a day. Most sleep 11-12 hrs at night, and nap still.
Leaving say 10 hrs awake. Out of those 10 hours 4 are spent eating three meals, snacks, baths, getting dressed etc
That's 6 hrs a day tops. A 1-5 year old is supposed to be active outside at least 3 hrs a day. That leaves maximum 3 hrs a day for reading, playing with toys, puzzles, drawing, baking, etc. That's hardly anything.
Especially when a chunk of that time is probably spent by many on school runs for older children, going shopping, visiting friends.