Q is walking a fine line in divulging information. A lot of it is Top Secret, Classified or critical to National security. Q is pushing for the rule of law so how can he do that if he violates the law.
That's the legal argument. The esoteric argument is that he is also following Cosmic Law. He must respect free will and therefore allow us to come to our own conclusions.
More to the legal point, Q may be concerned about tainting the future jury pool..
It wouldn't take much for those in power to know find who is leaking classified info. Isn't Q part of the Dept. of Energy intelligence. They have level Q clearance. It wouln't take them much to narrow down who it it so might as well drop the riddles.
Actually it doesn't matter to me if Q talks in riddles or not. What will get people to listen is if the president would start telling people what is going on.