When designers intentionally trick users into inviting friends or blasting a message to their social networks, they may see some initial growth, but it comes at the expense of users' goodwill and trust. When people discover they've been duped, they vent their frustration and stop using the product.

Habit-forming products alleviate users' pain by relieving a pronounced itch.

For an infrequent action to become a habit, the user must perceive a high degree of utility, either from gaining pleasure or avoiding pain.

Instead of relying on expensive marketing, habit-forming companies link their services to the users' daily routines and emotions.

If users are not doing what the designer intended (when users are investing time, effort, etc in your product), the designer may be asking them to do too much.

Reducing the thinking required to take the next action increases the likelihood of the desired behavior occurring unconsciously.

User habits are a competitive advantage. Products that change customer routines are less susceptible to attacks from other companies.