Zaps are cool because they make digital payments easy. It reduces the friction for tipping, which is great for exchanging small amounts for helpful advice, resources, etc.

Zaps can also be used to facilitate online purchases of goods or services.

I don't think they'll replace actual, priced services for content creators and the like. No one is going to get rich on tips, and people are hesitant to spend their Bitcoin while fiat currency is still the coin of the land.