Sure, NTS is preferable, but there are still places in the world where internet service is spotty / unreliable.
These little dongles (I spent 24 bucks, recall, on three because I couldn't be bothered to do returns on such a paltry thing) could be a real difference maker in an environment like that.
You do have to learn which messages to monitor though. There are dozens of them, with varying applicability. There was a class of them that seemed to be (for some reason -- maybe my bug or environment) about a half second off of real time. But, if you find ourself consistently off half a second for FT8 work, you can implement a manual correction or just switch messages. There are a lot of messages that return TOD. I found that a little obnoxious, but in the end, it's a minor hiccup.
I bought mine as a cheap experiment more than for real use. It also gives pretty accurate latitude and longitude and fairly accurate elevation (precise elevation requires a local correction because the earth isn't a perfect sphere and the eight dollar chip, at least, lacks the extensive data base that apparently exists somewhere to make the correction -- without it, you can be a fair bit off).