If they have no value, I'm sure there would be no incentive
In addition to what others have said: Believe it or not, some people do things for ideological reasons. There are Core developers and others who have devoted huge chunks of their lives to Bitcoin, and have much less to show for it in material terms than they properly deserve. There are people on this forum who make excellent quality posts, and receive in return via sig ads only a minute fraction of what they’d make if they were to spend the same time on commercial ventures—or receive nothing at all; some of the best posters don’t have sig ads. (Here in this thread: What do you think achow101’s time as spent here would be worth on the commercial market?) And for my part, though I haven’t (yet) done much of anything for Bitcoin, I myself am much less rich than you’d guess due to my innate propensity to act for principles instead of money.
Bitcoin would not exist without people who believe in Bitcoin. Its ancestry rose from the cypherpunk dreams of people who are ideologically driven. It was conceived and borne forth into this world by an anonymous individual who acted only for principles, and to this day has (for whatever reason) not touched coins now worth billions of dollars. It has been carried forward, improved, and maintained to this day by people who are primarily driven by ideology. Some of them also make good money—some don’t, but do it anyway.
If you want to see what a “coin” looks like when its development and maintenance is driven solely by material “incentives”, look to Btrash. That’s a good example—except that it’s a cheap knockoff which would never have existed at all, if it hadn’t been able to fork off the labours of love by people who believe in Bitcoin.
I've always been curious - who creates testnet coins?
This popular testnet faucet (one of many) has a current available supply of 29436.93 testnet coins. You get coins from the faucet, you use them to test software, and then you send leftover coins back to the faucet’s return address.
Testnet coins can be destroyed at any time. They can be destroyed by accident, via a software bug—or the whole testnet can be destroyed intentionally. This was the reason why we’re on Testnet3, as cannycassiopeia said. Testnet2 was intentionally destroyed because some idiots were using testnet coins as money.
Testnet coins are mined by volunteers. It has lower difficulty than mainnet, and a little quirk which drops the difficulty to minimum for the next block if no block is found for too long.
why doesn't the testnet coin immediately gain some form of value (since it is scarce and acts exactly like BTC)?
No, it does not act “exactly like BTC”. The whole network can be destoyed at any time, by accident or intention. Also, it is unlike BTC insofar as people who use BTC as money are smart, and people who use testnet coins as money are imbecilic scammers.
I'd imagine that testnet coins would still have a value of a few cents, right?
No. The monetary value of testnet coins is zero.
I don't know. You can collect 5 - 50 testnet BTC coins from faucets. So I don't think you can sell something that is freely given.
Well, people can. Developers can also respond to such a moronic thing by trashing the entire testnet anytime. Then, we’d have Testnet4.
Odd because I've occasionally seen people buying 1000 testnet coins for 0.001 BTC, and similar deals. Anyway, thank you for your help, I think I get it now.
That is a scam. Call it out as such.
Bitcoin Core also has a regtest (regression test) mode, in which blocks can be mined instantly. This is not a network; it is for testing and debugging code on your local machine, with a local instant-mine blockchain. Install Core, and have fun with godlike powers creating as many disposable blockchains as you want! Just don’t try selling any coins from them. That would also be a scam.
