Why build them?
The rationale behind them has to be different for each tier that your faction is in. I am interested in hearing your rationale behind the benefits of building them.
Give your faction's rank, level of walls you typically build and why you think it is a good expenditure of resources.
Mine
Top 250. Level 7 walls. We spend 6 mil dollars to prevent our opponents from scoring maybe 4k points. It does slow them down some and use up a few hits from scouting. At our level, I could careless how many points our opponents scores.