How come they never read from the Old Testament in Mass?

What are you talking about? They read from the Old Testament at every mass. Every mass I have ever been to contains:

(a) Two readings from the Old Testament, one of which is from the psalms and one fron another Old Testament book;

(b) a reading from one of the Gospels;

(c) (on Sundays and holydays) a reading from one of the other New Testament books.

For instance, if you were at mass yesterday, Sunday 6 September, you will have heard:

1. An Old Testament reading - either Ezekiel 12:1-14 or Ezekiel 33:7-11

2. A psalm - either Ps 149 or Ps 119:33-40

3. A New Testament reading - Romans 13:8-14

4. A Gospel reading - Matthew 18:15-20

Eleven Benevolent Elephants wrote: »

The Torah and Old Testament are probably very similar because Christianity didn't exist until God came to Earth.

The Torah usually refers to the first five books of the Old Testament, known to the Christian tradition as Genesis, Exodus, Leviticus, Numbers, Deuteronomy. They have different names in the Hebrew bible but they are the same works.