The reason it is phrased this way is because when a company misses forecast this usually results in the selloff of stock. This is generally the primary focus of earnings report reporting: the direction of the stock price.
I think that is also one of the reasons why public corporations are so heavily influenced by Wall Street in their decisions, and why they strive to reach certain quarterly goals in order to "meet the forecasts". If it was reported more like "forecasts miss the revenue", I think companies would be under less pressure from Wall Street to perform "at least as well as the expectations" every quarter.
I'm not sure what the phrasing of the reporting has to do with anything. It's an effect not a cause. The pressure from Wall Street is due to, well, the pressure from Wall Street. If analysts on Wall Street form a consensus around a company's expected earnings, then the market will price in that consensus. If that consensus turns out to be wrong, the market will (in theory) adjust accordingly.
In other words, if analysts are (in retrospect) over-optimistic, the stock temporarily becomes mis-priced and expensive (relative to an unknowable reality at the time) until the earnings report. Usually these analysts' look to the company's guidance (edit: or in google's case, the lack thereof) in forming their valuation. Add it all up and it's hard to see how there is pressure on a company to beat expectations, since they have the ability to set conservative guidance and try to get analysts to come to a consensus that is in line with the numbers that actually come up. If the company is performing poorly, they either depress the stock price in advance (under promise, over deliver) or later (over promise, under deliver) but regardless of when this happens if you buy into the EMH the stock is always trading at the proper value, behavioral economics notwithstanding.
For an example of an exception to this rule, see AAPL which routinely beats estimates yet sells off. One theory is that there is such latent fear that Apple is losing its mojo, each earnings report is a reminder that their growth doesn't compare to the old days, so investors flee despite their return on capital being extremely competitive.
Google's probably under less pressure than many companies because the dual-class stock structure makes them immune to takeover attempts.
I think a lot of the problem is that the stock price has many spillover effects. Recruiting & retaining employees is much harder when the stock is in the toilet. There's less currency available for acquisitions. It slants everything the press says against the company.
There was another story on HN today about how Marc Andreesen was dying to fund something that disrupts the financial industry. This is probably a major reason why: they wield disproportionate power based on made-up numbers.
Ah poor Marc, he only deals in real numbers. Wall Street is what it is but generally you can tell them don't expect much growth in the next 4-5 years and they'll adjust their expectations and share price. Coca Cola has a very different PE from Amazon and Google for example.
