This is true, but there's far more to it than that. I'm going to preface my story by saying at one time in my past I was technically a part of the massive, glaring problem that gave rise to locking, unlocking phones.
Many years ago! The Samsung Galaxy S3 came out & it was awesome. I think the carrier & other places were trying to sell it for $300 with a fucking 2-yr contract, or $700 street, etc. Now it's important to note that this was 2012, when the USD was worth at least half a damn & money was harder to get. So $700 outright is $953.78 today, no small fee. And a 2-yr contract?? Get fucked, my guy.
So I hop on Craigslist & I see this guy selling a brand new SGS3 for $300. Too good to be true! Or is it? I asked all kinds of questions, basically confirmed it was legit. Then I'm about to go meet him & he asks me, what color do you want? And I was like wtf?? How do I get choice? I think I got blue, idk? He asked if I wanted more phones, again I was flabbergasted, and I said sure my dad could use one... He'll want white.. He said he'd explain everything when we met, just bring $300 cash for each phone. And he did explain.
Turns out the guy was a bum. He was jobless, soon to be homeless, wanted fast cash & didn't care how he got it. These phones were easy to obtain, and he worked out a system where he could basically get infinite plans & infinite phones under his name. Once the phone passed hands...it became mine. And there was nothing the carrier could do about it.
He bought all his phones via a credit card, and he just racked up a huge-ass balance that he had zero intention of paying off. He's selling these brand new "under contract" phones for cold, hard cash. Thousands of dollars. Eventually everybody would get wise, his CC debt would default, he'd absolutely RUIN his credit. But he didn't care & he was planning to disappear.
Unethical behavior. If everyone acted the way he did, things wouldn't work. But at the time it really helped me, and my dad, and a few of my friends immensely. This is also back when smartphone upgrades were huge & actually meant something. We justified it as such: if we didn't buy the phones, he'd just sell them to somebody else. So why shouldn't we benefit?
Do you think this bum was the only guy that figured that out, that worked the system in such a manner? Nah. Who knows how much money the cell carriers & CC companies were hemorrhaging...and on bums, no less. ¯°_o)/¯ Lo & behold, a year or two later they rolled out cell phone/carrier locking. Your very expensive phone was locked down...until it was paid off in full. I'm sure it was in part because of the smartphone hustlers.
Now I am well aware this is Lemmy, the land of socialists, communists who want handjobs & $30 cutting edge smartphones for everybody. T-Mobile, AT&T, & CC companies be damned. But any costs or thievery done to these companies will eventually be passed on to the honest consumers to foot the bill. So...no. Unlocking phones for people who haven't paid off their contracts in full would not be good for the consumer. Because of thieves & bums.