For general testing of Bitcoin or applications built on it, very small amounts easily suffice (as explained above), and by using unnecessarily large amounts you are taking away tBTC from everyone else.
Precisely.
For the vast majority of test cases, are you testing that the code you are working on for *your* software/app is able to correctly transmit/receive transactions. The amount of the Tx is irrelevant (unless your code moves a decimal point...), it's getting the process to work correctly that counts.
Once your testing is done and the project is safe to use on the main
BTC network a true community supporter is expected to return tBTC back to the Faucets so they can continue to support code development.