why do people/game journelists keep calling mario a casual game?

[Nick]

ethomaz said:

guiduc said:
Mario roots aren't casual, and he sells like monster.

Mario has always been casual.

My colleagues on primary school know and play Mario, not to finish. They played once a week or month just for fun or to show a friend who had a game.

That in 1990.

You know you can play a hardcore game casually and a casual game in a hardcore way right?  I mean... what you just described were people playing a game casually, not a casual game.  Some people you know played Mario in a casual way, a lot of people I know play Mario in a hardcore way. 

Casual and hardcore can describe gamers not games.