Amazon prime - who would pay for this??

Here are the benefits of Amazon Prime (from their website)

- Unlimited Express Shipping

- Free Two-Day Shipping on over a million in-stock items sold by Amazon.com

- Overnight Shipping for only $3.99 per item—order as late as 6:30 PM ET

- Ship to any eligible address in the contiguous United States

- Effortless Shopping

- No minimum purchase required

- No need to consolidate items to save on shipping

- Convenient Sharing

- Share the benefits of your Amazon Prime membership with up to four family members living in the same household

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All this for $80 per year. It's not available to businesses.

So, why, WHY, would anyone pay $80 per year to get their books shipped free via 2-day shipping (no minimum order) vs. 3-to-5-day shipping with a minimum order of $25.

Seriously, I don't get it. Please, someone explain it to me. :)