When parents ask me why their children can't make progress, I always ask how many chess tactics problems their children are solving everyday, how many games their children play online, how many tournaments their children have been playing, etc. They would pull some numbers out of their head and confirm me that their children have played. My followup question is: everyday? Then comes the hesitation, and some answer a few days, twice a week, or one day a week.
They have no log to back them up, so they can't tell exactly how many problems their children have solved, and how many games they have played. They only have some fuzzy ideas that their children have played. That's very bad fuzzy ideas. Chess, like math, requires exercises everyday! If they don't have a log, they never know how many their children have done, and what need to work on.
When the child is under 10, it's most possible that the parents will shoulder the task. They have to jot down the number of problems, the number of games, the number of tournaments, the number of videos, the number of hours, and etc. When they have numbers, they can tell how fast their children is moving. Sometimes their children might move in the appropriate speed, then no worry. Sometimes their children are moving slower, then spend more time on chess.
For example, if they have a chess puzzle book that contains 1000 problems, assuming they think 10 problems a day is a proper speed, which means their child should finish the book in about three months. If they record the number everyday, then they know when s/he moves faster, when s/he moves slower, and when s/he skips a day or two. At the end of 3 months, they can tell if s/he is on target.
It's so critical to maintain a training log, even for adult chess players. We can't play the numbers by our ears.