I don't agree with most of crypto users who say that tbtc is worthless, if it's worthless, give me 100 right now to test, don't you have?
Rather than worthless, i would say it shouldn't be sold since testnet isn't meant for that since there's cost to mine tBTC. That's why testnet3 is the current test network since people attempt to sold tBTC in past.
I offer it for free, but some money has to be put on collateral in case he spends it or goes offline.
Then it's not really free. If, to acquire them, he needs to risk losing money, there's definitely a possible hidden cost. Especially for coins that are meant to be tested, hereby to be lost either accidentally or deliberately.
I agree. In such case, there are another member who already doing that such as
https://bitcointalk.org/index.php?topic=5306684.0.