What is the most basic reason christians began to build church buildings, or have them built?

I don't know the logical answer for this, but my theory is that they built church building so that Christians would have a "safe" place. They could go into that building and know that they were safe from all of the world's drama, and they could focus on their relationship with God. 

Evangelist decided to spread the word of God and worship in larger groups so it was like a community of church families