Is there a name for the type of video games that encourage to play for short periods of time but regularly?

The term that comes to mind, as @djsmiley2k mentions in the comments, is casual. While not a perfect source, Wikipedia describes a casual video game as (emphasis mine):

• Extremely simple gameplay, like a puzzle game that can be played entirely using a one-button mouse or cellphone keypad
• Familiar genre, like a card game or board game
• Allowing gameplay in short bursts, during work breaks or, in the case of portable and cell phone games, on public transportation
• The ability to quickly reach a final stage, or continuous play with no need to save the game
• Some variant on a "try before you buy" business model or an advertising-based model

Whilst it's possible to play a game like Animal Crossing , Plants vs Zombies or Angry Birds for hours on end, it's also possible to play for a short period of time.

The Steam store also has a tag for casual games which lists Plants vs Zombies and Angry Birds amongst others, though doesn't go on to define what a casual game is; however, Steam tags are user-defined