You sort of missed the boat. Transparency, allows pilots to make better decisions about the experience, familiarity, availability, health status, bidding preferences, swap possibilities, etc. While there are valid reasons to block your calendar from other pilots. Very few of those reasons are long term issues. Since only the pilots use this calendar, the blockers are only blocking other pilots. Thereby the conclusion drawn, that if you are blocking your calendar you are doing things that you don't want other pilots to know what you are doing. While always an issue, in contract time.....
We do have swap/drop etc boards and they work great for general swaps/drops, etc. But if I wanted to swap or drop, I'd look for specific people that could help me rather than a general, feel free to screw me, on the trip trade boards. Easier to solve your own problem than to hope someone will help you fix it.