Or perhaps it's simply this: Humans like round numbers. We always have. In nearly all cultures on earth, you'll find relevance attached to (usually) the numbers 2,3,4,7, and 10, and their respective multiples. I admit that the relevance of 16 being attached to Preservation is not explained by this, but many examples are.
As for Roshar, I see this as correlation without causation. Almost any of those instances could be the cause of some or all of the others, or they could all be the cause of another, external factor. So ten is not necessarily a special number, it's just that once there was 10 of one thing, and in emulation or as a result, now there are 10 of many different things.