Why should any retired government and military official retain a security clearance and get access to classified information if they are not performing duties that require a clearance?
Retaining your clearance is common, not just with high level intelligence people. as an officer every one of your son's and daughters will have at least a Secret Clearance. Many depending on their job or branch will have a higher clearance. For many this is one of the draws of branching MI, getting the Top Secret Clearance. Once they decide to leave the service the clearance does not just disappear, it goes with them, it's one of the things that makes them attractive to employers that require a clearance, the employer does not need to pay the ten's of thousands of dollars for a clearance they already have. Even if they are not hired by a firm that requires a clearance they still have it until it times out.
One of the main reasons it's good for these top intel people to retain their clearance is so they can be tapped for their experience by the new intel leadership. When new intel people come on board they do not have much info other then what they are briefed on, they need the former intel officers input as they get up to speed. If former intel were to lose their clearances as soon as they left their office they would not be of any use to the current intel officers and a lot of valuable information would be locked away. A security clearance and the First Amendment are not mutually exclusive.
If they followed your thinking then not only intel officers would leave with no clearance, every member of the military would lose theirs as well, none of our kids would be very happy if that happened.