As with Christianity, Judaism, etc, different people interpret their scriptures slightly differently.

Some people believe it is OK to drink if they don't pray whilst intoxicated, some think it is totally fine to have a drink and some think that even consuming trifle with a bit of sherry in will send you straight to hell (most alco free beer still has 0.1-0.5% alcohol in it - such a low amount that drinking enough to get you drunk would kill you first).

Basically, you can't group people all together, even (or maybe especially!) if they are the same religion. If people of the same religion were a homogenous group, Glasgow would be safe to walk through on Saturdays.