A slogan is meant to be a novel, attention-getting expression of what’s usually an obvious, self-explanatory idea or premise. To drive home its point, though, a slogan makes clever use of a suitable rhetorical device to emotionally connect to the readers or listeners and circumvent—short-circuit, if you will—their rational thought process. In particular, the bank slogan you presented, “We do banking, you do life,” uses the rhetorical device known as repetition—it repeats the key word “do” in two parallel clauses to reinforce the emotional appeal of this otherwise bland, matter-fact statement, “You can enjoy life better by banking with us.” On the other hand, that music bar slogan, “Why would you go anywhere else but Boracay?”, uses the rhetorical device known as rhetorical question—asking a leading question for which no rational answer or objection is expected, only the involuntary assent of the reader or listener.
Now to your first question: Why do those slogans seem wrong? Upon inspection, we’ll find that there’s really nothing grammatically, semantically, or structurally wrong with them; they only seem wrong because their wording deliberately departs from the humdrum, unmemorable way that their idea or proposition is usually expressed. In short, they are crafted for their quiet shock value, the better to circumvent any rational objections to them. In the case of effective slogans, though, acceptance of their idea or proposition usually follows as soon as the shock wears off.
This brings us to your next question: What must be done to correct those two slogans? Nothing really by way of better English, for their English is airtight. The way they say things may make you flinch and may rankle your sensibility for quite a while, but ultimately, their success as slogans will depend on how well you remember and accept them—and allow them to steer your purchase decisions in the direction they suggest.
