You pay your dues, and two day latter you are booted. When you ask why, you are told that you did not pay your dues. How do you stop this type of abuse from happening? If dues were TP, then this is dealing with peoples real life money; and then Turbine would need a way to deal with this type of abuse. How would Turbine deal with claims like this; refund the dues, reinstate the booted player? What about people who claim to have paid their dues but did not, and were booted for other reasons, they are simpley trying to get something for nothing?
If they put in a way to track and/or collect dues from members, then there will be people who will try to find a way to abuse it. If people are or are trying to abuse a feature Turbine has put into the game, then Turbine has to have a way to deal with that. Which in my opinion just means more time that the Devs and/or DMs have to take away from other parts of the game.
In my example about the guild who did collect dues. Dues where not mandatory, we paid what we ould when we could. The guild had a three strikes your out rule, for breaking guild rules; and even then three fourths of the officers had to vote to remove said person from the guild, and any officers caught breaking this rule was automaticly removed from the guild. This guild spent a lot of time outside of the game finding what worked for them.