Why is there not a limit for in-app purchases!!

My child is homeschooled (for medical reasons), and for the past week and a half, he borrowed my phone to play the game during his breaks and sometimes at night. I thought nothing of it since he returned my phone every time. Somehow he manages to spend $1000 without realizing it. Then I receive a text message from the bank due to excessive spending. Why is there not a 2 Factor Authorization for excessive spending? How come the bank has better detecting skills than Apple itself. Maybe set a limit to prevent this kind of problem at $150. What is worse is that I have been denied my refund. I much rather lose $150 than $1000. I'm pretty sure several parents have the same issue. Set a limit Apple!