Online Ads

I've noticed more and more ads on sites such as the New York Times. You click on an article, but have to watch an ad first before the article will come up. But what I don't understand is that the ads invariably have a tiny, little link up in the right hand corner that says "skip this ad" or something similar. Why does the New York Times offer you a way to skip the ad? How does that make sense from their perspective?

Stuart Buck