There are so many reasons to go into space that is beneficial to humankind:
A possible answer to the prospect of overcrowding
The manufacture of drugs and antibiotics in a weightless and sterile environment
Collection/distribution of new types of fuel sources (radioactive, solar or even antimatter) to alleviate the problems associated with fossil fuels
New inventions (velcro was developed as a direct result from the space race, as were many types of polymers)
Learning more of our world from the lessons of others - Venus' runaway greenhouse effect, Titan's ice age, or Mars' thinning atmosphere
Seeing our planet from a different perspective - from orbit - to repair or alter hazards to our environment (charting the migration of algal blooms through prolific fishing zones, or locating incidences of crops with fungal infections using infra-red technology in space, so treatment can begin)
The advent of the International Space Station is not only a symbol of goodwill and co-operation to the world's space powers, but also acts a springboard to future important missions to the Moon, Mars, and - perhaps - beyond. Past missions have been deemed "cost prohibitive", compared to the cheaper option of using the ISS as a launch platform in the future - the energy saved by not having to make escape velocity from Earth greatly increases not only the range, but also the speed, size and amount of payload that may accompany an interplanetary flight.
The Moon may also act as a platform in future space missions - with 1/6th the gravitational pull of Earth, a large quantity of ore, and the
possibility of water on the Lunar surface (collected in craters from the alleged past impacts of comets), a permanently manned base on the Moon would be instrumental to any further space exploration.
It's our inherent nature to be inquisitive. Who are we to stifle that desire in us all?