I think this attitude is due to a lack of competition that has resulted from the stagnant politics. Hopefully now that all other exterior threats have been effectively mitigated, the Syndisphere will begin to split up and politics can move out of the quagmire of their present state.
The short-term payback from taxation is seen by the alliance as a whole benefit. Alliances provide the security in which economies can flourish. Without the competition to fuel the need for security, people begin to question why their money is going to other nations.
The long-term is fairly obvious but the issue is that the concrete payback will only come after a long term period. Once everyone is decent sized, alliances can then afford (and advised) to refocus on making sure their upper tier continues to grow. It's like an inch worm. The smallest members grow to then fuel the larger, then the cycle repeats.