How does the seller benefit in an all cash deal?

[Cody W.]

I've just listened to podcast 283 with Paul Thompson and he mentioned a scenario where he offered somewhere around 70% of listing price in cash to the seller because they wanted to buy an RV and travel the world. 

What is the benefit of this deal to the seller? I feel like if you could just wait a few weeks for the deal to go through the traditional financing route you'd end up much better. Is the convenience of a faster deal worth several tens of thousands?