The answer is no, it is not a good idea to hand out answers to trivial problems, but that doesn't mean we won't do it. Many MathOverflow users find it very difficult to resist the urge to write a solution to a problem. This is actually one of the root causes for MathOverflow's success: Mathematicians love solving problems and, to fully savor it, a solution must be posted somewhere... like MathOverflow!
This source of MathOverflow's success is also a source of problems, like the one you point out. Various etiquette rules regarding problem solving have similar consequences, such as the silly rule that only the first solution counts. So the answer to your question and a lot of related questions is always the same: it might be preferable not to do this or that, but it would be equally detrimental to enforce a rule saying not to do this or that. This is why MathOverflow historically has only one rule: you must wear pants!