Who's been drinking in my bar?

Something strange is happening in Doha. And while that in itself is quite normal, this is a new kind of strange. The Qatar Tourism and Exhibition Authority and Ministry of the Interior (!) requires that access to any bar shall be on production of a valid ID or Passport. Originals only, no copies. But it is not enough just to flash the card. The details, name, ID number, date and time, are to be manually entered into a log-book. But what is the permanent record for?
Not to keep out illegals, because that can be done without the log-book.
Not to identify illegals, because by definition only legals are recorded.
Not to find who is drinking alcohol because no record is kept of what customers drink.
Not to discourage national dress in the bar, because no record is kept of what guests are wearing.
Not even as a security check of who is present, because no record is made of when guests leave.
Then there are the usual anomalies: what is the difference between a bar that serves food and a restaurant that serves alcohol?
Because there was no explanation accompanying the ruling, rumours are rife. Some say it is a 'record of shame' to discourage nationals from frequenting the bars. But then why register the expats? Others that it is to help police track offenders who commit crimes shortly after leaving the bar. That makes no sense, so it's probably true. Or can any readers here offer a better theory? My money is on pointless prurience.