Why were the catacombs used for worship, especially in the West?

The term “catacomb” is probably derived from the Greek words, kata kumbas , which mean “near the hollows.” Roman Law used to allow burials to be conducted only outside the gates of cities, and so these catacombs were built under suburban roads. They were regarded as sacrosanct, meaning that these roads must not be attacked. That is why some Christians used them in some countries, especially Rome, as places of worship during the times of persecution.