It's called earnings management, and it's legal, even if not entirely honest. There are several reasons why a company might do this.

 1)  Lots of stakeholder’ have an interest in a company’s performance. They are happy to see increased earnings.

 2) Window dressing: If a company is looking for new financing, they will have an easier time getting it if their financials look good

3) To meet internal targets: of a company or just one of its departments

This practice is called “income smoothing,” and its purpose is to make for a smooth trend in earnings over time; investors and other stakeholders  like to see a continual upward growth in earnings.  

 One method is called the “cookie jar reserves.”  Management recognizes estimated expenses in a year when revenues are high, so fewer expenses are recognized in a quarter when earnings are lower.  Another way to accomplish this goal is to defer revenues for “tougher times.”

Almost all corporations do some form of “income smoothing,” It’s perfectly legitimate, even though it really doesn’t accurately portray a company’s earnings in a given quarter or year.   The part that sucks is that its very hard to detect; a company does not have to detail in the notes to the financial statements which expenses and revenues are being deferred or not recognized.

Enron cooked the books legally as well the government aloud them to use a risky accounting practice called "Mark to Market Accounting"

Enron was still following the law but what they were doing was ridiculously unethical