This is the problem with capitalism's motto about building a better mousetrap and having the world come beating a path to your door.
Some perfectly good and very affordable mousetraps get cast aside and taken off the market because everybody's clamoring for the newest coolest thing-- which may not have any practical benefit over the old thing.
I don't think that applies in this case.
The 350 Legend solves a problem: It's legal for hunting in places where 35 Remington and other bottleneck cases aren't. It's got substantially more effective range than a 357 Mag rifle, which also has very limited availability in guns other than lever action.