I Want to know why people still suffer from the lack of food, water and medicine in the 21st century?

It probably is because they can't afford it or they just don't care.

Because people increased and the sea is almost empty. Our mother earth is destroyed..

If you have money you get all this and if you haven't there is nothing . I don't think that people attitude may change in 21st century.

Part of it is greed, but most of it is the blind desire for power. It causes puppets to be "elected" without the will of the people in nations that are supposedly republics, and those holding the strings are special interest groups, big pharma, etc. It's a long answer and this is just a scratch.

War, politics, drought, poor government, overpopulation, lack of education, export of trained doctors and nurses to richer countries. the reasons I fear are many