This is a really good measure that will reduce the abuse of your Testnet; I don't know what the point of them draining the Testnet Bitcoin faucet is. Do they think these are real bitcoins on the main networks? lol
There are a lot of crypto scams happening nowadays, and this testnet bitcoin can be used to scam others who are not aware that it's a testnet BTC that can't be used for anything and can't also be traded.
I have come across such a scam before where I saw someone's Coinbase wallet being loaded with one of these testnets of bitcoin, and the person said that it's real bitcoin. What surprised me about that is how they were able to make price reflections on that testnet BTC, like the same bitcoin value is showing and displaying in that testnet BTC.