I'm sure the problem was complaints from guests who were escorted out of the park because they hadn't paid the extra money for E-nights. Many people aren't happy paying $50+ for the park as it is and would become enraged if asked to pay another $12 to stay in the park that they have already paid to be in. I know if DW and I travelled with her Grandpa and we asked him to fork over an extra $12 for E-nights, it would take us days to get him to stop complaining about it.
People have thrown out the option of extending park hours, but if extending hours doesn't increase attendance enough to justify the extra labor costs, then that is no longer an option. I know it sucks to think of WDW froma business point of view, but when you do look at it that way the numbers don't lie.
With extra hours not being an option what Disney is left to compare is the profit generated by E-nights vs. the negative perception created with guests that have a problem with it. At $12 a pop x 5,000 guests it's only $60,000 in revenue for Disney. Considering that Disney's most important asset is it's brand equity and that the total revenue in the parks last year was almost $6.5 billion, it's very easy to see why E-nights have gone away. In fact, it's very hard to see them ever coming back except during times when the park is already open late and the crowds thin out before close.
Personally, when faced with a choice of paying $12 to ride the same number of rides at night that I paid $50+ for during the day, it's a no brainer for me. I think the $12 for an E-night is the best bargain I've ever seen at WDW. It a shame that people have complained about it enough to make them take it away. Unfortunately the only way to change the negative perceptions of the people who don't like E-nights is through education. Because it would cost money to educate people on why E-nights don't hurt regular guests (and the costs for educating guests would completely wipe out any profit gains from E-nights), there really isn't an easy solution to this.
With all that being said, I still think you should call or write and ask for them to bring back E-nights. I like them and I want them back!!
-DH