Why do Catholics drink Alcohol since it is forbidden in the Bible?
There is no Bible passage which says that wine or alcohol are evil things in themselves. (Psalm 104:15) speaks of wine as one of God's gifts "to gladden the hearts of men". Christ changed water into wine at the marriage feast of Cana, (John 2:1-11) and drank wine himself which led to the Pharisees calling him "a glutton and a drunkard" (Luke 7:34. Paul tells Timothy: "No longer drink water only, but use a little wine for the sake of your stomach" (1 Timothy 5:23).
At the same time the bible warns against the abuse of alcohol and utterly condemns drunkenness. Proverbs 20:1 says: "Wine is a mocker, strong wine riotous, and whoever is led astray by it is a fool." St. Paul tells us in 1 Corinthians 6:10 that "drunkards...will not inherit the Kingdom of God." I am sure that you yourself will have seen the effects of the abuse of alcohol – serious motor accidents, fighting in the home, broken marriages, poverty, etc.
If you can't drink in moderation, stop taking alcohol altogether. Sometimes people who do not take alcohol regard themselves as closer to God than those who do. This is unfortunate. Signs of closeness to God are kindness and love of others and not taking or non-taking of alcohol.