Why not devote paragon points to main stats?

In this video, prepared by a fairly prolific D3 YouTuber, he reviews a build in which he intentionally does not put paragon points into his main stats. In fact, in every video I've seen of his, this is the case.

I've played D3 on-and-off since its initial release and I cannot, for the life of me, figure out why he's doing this.

Why wouldn't one use all their paragon points?

He's not putting paragon points into his main stat, because he's showing off a build.

Having almost 3000 extra points in main stat would make the build much stronger than it is and it might not be viable without such a high paragon level. By leaving his main stat unchanged, he can actually show off the build without the bias of extremely high paragon level.