What do you think a NAS is used for? In my case I've run out of space on SSDs, which I prefer, and I can't afford to start buying terabytes of SSD storage. A trade off is to shift as much of my storage, including things like virtual machines which occupy a lot of space, onto NAS storage with a high performance network link. Not quite as good as an SSD but a bit better than a typical single hard drive.
10Gb network cards sell for $17 a pop, people can buy two and do a point to point link to another machine, like a NAS, for peanuts - there's not much good reason to look a gift horse in the mouth.
So to get around to addressing your dubious point that not all transfers benefit from a 10Gb link, well not all your transfers will benefit from your 1Gb(?) link - but I'll assume you aren't going to downgrade to 100Mb even though it might save money.