Wow,this is really an interesting question.

A Museum is a place full of historical artifacts, scientific, cultural interest are kept for reference and for sight seeing also..

Temple is a place of worship and prayer for those seeking the face of God.

Not everyone are spiritual and most people are not religious, they don't even believe in God .

So they would rather go to the museum where they can have fun and also for various reasons such as research and learn about the ancient world than be in the temple.