It's not SUPPOSED to have value, that is true, but it's still a functioning PoW chain which means you need electricity, hardware and money to mine. If it had NO value then faucets would give away 100 coins for free, but they don't because it costs money to mine, and it's not easy to obtain large amounts when you need a modern ASIC to mine testnet.
I have to disagree, the only reason why faucets are not giving away 100 coins for free is the fact that getting tBTC became difficult and costly, and why is this the case? it's because of greedy people hitting the testnet with ASICs, so pointing people to hammer the testnet with more ASICs isn't going to solve the problem, it will only make it worse.
It should cost less to mine testnet coins than to watch a movie , speaking both bandwidth and electricity, so saying that it needs "electricity, hardware, and money to mine" is technically correct but put in context is just wrong, you may not be intentionally doing it, but comments like that give the illusion that tBTC must have some inherent monetary value to make worth more than it was intended to be.
Also, there is a technical issue with testnet due to PowAllowMinDifficultyBlocks whereby it takes the last block's difficulty and assumes it was the average difficulty for the entire epoch which then sets the entire new epoch to difficulty of 1 if the last block of any given epoch is 1, or if some asshole miner sets the last block timestamp 20 mins into the future.
When ASIC miners are hammering the testnet while its diff is 1, thousands of blocks will be found in a second, this causes blockchain reorg, a very resource-consuming process, you can imagine the resources it takes to reorg millions of blocks and then get hammered again with another blockchain reorg while in the middle of the first one, nearly every node that uses memory for that purpose will freeze and go out of service, this happens with more than 10% of all epochs, all due to the fact the greedy people are using large ASIC gears on testnet.
I understand that some honest and good devs just want a few tBTC to test their shit, but two wrongs don't make a right, it's like saying "If I don't do it - someone else would", it's fine if you want to be another asshole in the Bitcoinverse, but don't use it as an excuse to do the wrong stuff.
Even if you desperately needed those coins, as a dev, you could be aware of the "dirty" ways you can obtain them in secret, it's still a lot less harmful than going public asking miners to rekt testnet so you can test whatever software you are working on.
Furthermore, for the vast majority of tests, you can use regtest or even better, use Signet.