Less Work, Higher Salary

I still cannot understand why most of people are always like this: they want to be paid higher salaries but with minimal work; I've been observing my co-workers (I'm new to this company) and this is the trend right now, people are complaining too much in what they are doing and getting less paid. I've observed this especially to newly graduated people; they don't care anymore if they learn a little, they are more interested in earning MORE; sometimes I also feel that way, sometimes I'm asking myself why am I helping this people and sharing them the things that I've learned event though I know their intention - resign after a year or less to get a higher salary. There are also some co-workers that will little by little they will pass their responsibilities to you then... resign! Well... life must still go on.