Why do we have Temples and Shuls?

Are they here for support until we go home to Israel?
Are they here to provide comfort to those who are born and die here?
Are they to help us find the way to HaShem?
Are they here for us to learn how to live as a community or how to live with another community of non-Jews?
Are they here for life cycle events?
Are they here to help us keep the faith until the 3rd Temple is built?

Avi