What is wrong with putting price timeline in e-commerce sites?

Question

Why don't e-commerce sites, e.g. amazon, include price timeline charts for their products so that users will be persuaded on the discounts? Does it incur any culprits for usability or even for sales? It sounds so tempting for a customer to check the previous prices of a product, doesn't it?

edit: To be specific, I hate the shops that apply anchoring effect/bias to customers. And I thought user satisfaction will skyrocket in the event that I can show the real price changes. But after all, this is the nature in commercial; making people feel happy out of shopping. Besides, as Vitaly outlined below gracefully, it might draw people into hesitation.

And another article related to Anchoring effect.

Answer 1

Nice question. I can think of a few reasons.

1. The contract with the vendor may forbid it. Vendors have all kinds of weird ideas. Some don't let ecommerce websites disclose even the current price unless the user clicked on the product and asked for it specifically.
2. In general, the less info the buyer has, the less he feels in control and the more vulnerable he is. Which means that he might buy something :). See this article on how Ikea floor planning disorients the buyer and makes him feel helpless - and buy stuff! I must say though that more common is the opposite approach to e-commerce best practices, which says that the user must feel in control, which increases his trust in the website and encourages him to buy stuff.
3. It reveals all the tricks of "special sale, just till the end of the week". As often as not, there's no special sale and that's the going price - but we don't want the buyer to know that.
4. Let's say the user compares and sees that the price was low and now it has gone up. He won't buy because he feels that he had missed his opportunity. Would you buy something when you know that it has just gone off sale?
5. The opposite case is not much better. If he sees that the price was high and now it's low, he might be tempted to wait around and see if it continues to drop. Why buy now if the price seems to be declining? Same as on the stock market.

Whereas today, with just the current price, all these psychological dilemmas are spared. That's the price, it happens to be 20% off - only today and just for you - so buy now.