Humans are required to install and fix things in space that robots have not yet been designed for.
Humans can handle unforseen problems that could occur in space exploration.
Humans can perform more extensive and in-depth research since they can analyse what they are collecting as opposed to just bringing it back to earth.
So much more can be learned by having humans in space that can reason, react and analyse.
Space exporation began because humans wanted to explore for themselves and push the human boundaries as far a they could.
Today, space exploration still has the same purpose. Not sending humans into space would defeat the primary reason of space exploration.
