The low payout of faucets is a problem. Saying you don't need larger amounts for testing is a myth repeated by many. Bitcointalk runs on PHP and MySQL and a large portion of the web still does. MySQL's max integer limit is 2,147,483,647, and it's best practice to store bitcoin amounts in satoshis, not floats. Therefore you need at least 21.48 tBTC to test your database and all aspects of your site and/or connected apps can handle integers larger than 32 bits.  Is a deposit larger than 21.47 BTC likely? Probably not on most sites, but it's not impossible, and that's the last order you want to screw up when you switch your site to mainnet because you didn't test your site properly.