Some people never let their shiba off the leash. In fact, some people will tell you you mustn't ever let a shiba off the leash, because shibas don't recall.
Shibas absolutely recall. But, the less you let them off the leash, the more they're going to try and make the most of it when they do get off the leash. So if you never let your shiba off the leash and then it escapes, good luck catching it.
The other reason shibas need to be let off the leash is because they're very, very fast dogs. Tinky-Winky, who's ten years old and the mellowest shiba her breeder has ever known, can run 40 km/h on a sprint, and 25 km/h over several kilometers. And not only she can, but she needs to. Back home where we get two or three 3 km off-leash walks a day, she will trot much of the time even off leash. Here in Yellowknife, where we can only have off-leash walks on the weekend, she runs the whole time she's off. And this is rough terrain, mind you. She doesn't care. She zooms over the snow and rocks for two hours. At some point she'll let me know that she feels it's time to go back to the car, but she still runs all the way to the car.
Off-leash is really the only way for her to get enough exercise, because not only I can't move as fast as she does, but also she covers considerably more ground in her meanders than I do, and if I had to walk that far with her on the leash, I'd probably trade her for a pug.
I love my dog.