In an effort to make the site better and increase users, the 140-character limit has been lifted for direct messages. Before with the 140-character limit, users felt limited in how they can express themselves with the person they are communicating with. But no, more emojis, more pictures, and text will help you be more expressive and get your point across.
This character removal only affects the direct messages. As far as regular tweets go, they will still be capped at 140 characters.
Twitter currently has 300 million users versus its competitor Facebook with roughy about 1.4 billion.
Source: Yahoo Tech