My wife and Father always want me to save. But why, Savings or Invest?

Working in IT company from over one and half years, which I am loving it. The vision and compensation both inclining towards the best.
Having the house under the rental one unit and living in other is a mortgage as well. Overall, the situation is nice, may be only to me but not to my parents and wife.
Out of what, I am earning, I am spending 40% on living costs with a…