Because it is possible to create some transactions but I will have to then manually send all the transactions back to the main address, which would be a lot of unnecessary work if the actual value of tBTC is 0 USD and therefore it should be easily available.
Unfortunately, the days of wasting testnet coins are long gone 
Quote
Also I want to have some tBTC for future projects for example open a LN channel and just did not expect that it would be so hard to obtain the needed amount.
I keep a small amount for such testing, and indeed always closed the channels and returned the recovered the coins when I was done.Quote
I hope if this doesn't stop there will be just a second testnet or something
As far as I know, Bitcoin is on it's third testnet reset already. You may be able to use regtest instead of testnet.Quote
all help regarding testnet mining will be appreciated
There's mocacinno's testimage on the cost of mining testnet.