Are you allowed to bring your own drinks to a pub, rather than buying drinks there?!
Typically the only time you can do this is if the establishment is a restaurant that features a 'BYOB' (bring your own bottle/booze) night. Some restaurants do this for special events, but normally will charge you to bring your own alcohol (the fee is referred to as 'corkage' and typically applies only to wine) to make up for the revenue lost because you're not buying from them.
BUT, based on the phrasing of your question, i.e. a Pub.... No, you cannot bring outside drinks into an establishment that serves alcohol, and you cannot leave with the alcohol they sold you. If you are caught, you can expect to be bounced or at the very least have your alcohol confiscated and get some flak.
Honestly, the real problem with this in practice is that as you drink, your judgment is impaired, and it gets harder to hide your rule-breaking from the people in the pub. So maybe when you entered you were suave and hid your flask like a ninja, but after an hour or two you aren't so smoov and get busted. ("How'd that happen?") Use your best judgment, especially if you intend to return to the pub in the future!
all advice above is based on U.S. law. Actual mileage may vary.
Ermmm, that's how they make their money.
If it's the same where you are as in the UK if a pub has a license to sell spirits then it's illegal to drink your own in there
Many times you can't even bring a snack.
No you can't
No. They are in the drink business. You should purchase your drinks there.
Depends on what their license entitles, as well as your age + local laws.