Are manned missions necessary and feasible to other planets and exo-planets?

Is it required to endanger humans to explore other planets and especially later exoplanets?
Is it more expensive in time, money and labor to create environment and tools in spaceships suitable for living creatures/human beings, than creating robots instead?
Is it not time consuming to prepare men for such missions for their living and working on the surface of a planet?
Is it not more cost effective and faster to avoid creating such factors, but creating travel and purpose/target means instead?