Why do houses sell at 70 percent of value?

[Tyco Bronye]

When I bought my first and only house I looked into how much I should offer and I read from various sources that you should not offer more than 10 percent off the asking price or your offer will be rejected. In my own experience I've only purchased my own house that needed rehab that I bought for the listed price. Before that I made an offer on a house for listed price that had multiple offers and mine was not accepted, in other words someone offered more than listed price.

So it begs the question: why are houses sold at 70 percent of the value?