Most humans simply do not like the concept of infinity when it is applied to causation.(we like it fine when considering an afterlife) We have no idea whether the notion of a 'first cause'- God or otherwise- makes sense, but that doesn't stop many from making declarative statements.

We have the grammar/language to describe things we don't have the senses to experience or comprehend. It's also a great temptation to construct a logically consistent schema that no one can prove 'wrong', whether it has any basis in reality or not.....sometimes there is money to be made in the enterprise.