Why would you want to buy an adjustable bed?

They're useful for several things, such as:

treating acid reflux and sleep apnea.

adjustable bases can also improve blood circulation, promote breathing, and relieve lower back tension.

here's a great article:

http://ezinearticles.com/?Adjustable-Beds-and-Acid...

but yes, they are purchased a lot for lifestyle uses such as watching tv in bed, reading in bed, using your laptop in bed, etc. A lot of higher end ones have massage features.

If one is so spoiled that they think that they need a bed that adjusts rather than prop up pillows of reading in bed and other related thing. I think it's pointless and a waste of money.

they are very useful for the elderly, or people who experience discomfort when lying down or need to lie down for long periods of time. It enables you to adjust your sleeping position to one more comfortable, and to get out of bed more easily.

Well, sometimes people buy them if they have back pain. And other times, people just think they need them, when they don't.