Maybe because if they frequently forgive mistakes of users, they'll face mistakes from them regularly and it will turn into a mess for them. To my mind, in such a case, it's better to block users from depositing in this specific network than not to refund them when you have access to that network.
How do you block a user from depositing in a certain network if they are going to copy an Ethereum address and the deposit USDT on Optimism, of which Optimism network may not yet be supported but the ETH address is compatible with that of Optimism.
My point is people will still make mistakes whether there are blocks or even warnings.
My point is that, when you deposit USDT for example, you can choose BSC network, TRC20 Network, Aptos and etc. Addresses are different for each network and when you type the address, the system automatically detects the network and blocks your from depositing though this network.
Its better to have this kind of warning on where they remind people to deposit or withdraw their funds on their preferred network. Since with this for sure that they can save lots of money also time if they have reminder on things that they need to do.
For sure this issue might gonna happen again to other people especially for those who didn't check well the network they are sending.
But what's good thing to look on the situation happened is we see that Roobet doing good for solving the issue of recent user posting his claims here.