Basically there are not many philosophical questions to ask. We have already asked some of the most important ones. But history presents us with many different answers to each question. So it is easier to ask philosophical questions than to answer them.
In the first letter that Alberto sends to Sophie, he explains that philosophy is very simple. There are not all that many philosophical questions for us to ask. The point, then, is not simply asking the questions but rather coming up with some sort of a solution for them. And that solution will not be easy. People have been trying to answer some of the questions for thousands of years and we can take into consideration what they already said, but in the end the answer must satisfy us personally. Also the role of historical context becomes important. Freedom in ancient Athens meant something different from what it means now simply because slavery was an accepted part of life back then. There are aspects of every historical period that by current standards are judged wrong, and this means that we too will someday be looked upon as unjust or immoral in certain ways. Philosophy moves with human history.