First, they want a feature which was part of an expansion in a previous ideration (doesn't need to be TS3, but it is most of the time), then, when said content will be released, the same people complain about it being a repetition of an older ideration...it happens with every single pack for TS4 that releases. And then, when finally something new releases that wasn't in any previous ideration, people complain AGAIN, mostly things like "where are pets? Where are seasons?"
The ultimate solution would be that the devs just add things like seasons and pets already in the base game, but these packs make so much money everytime that I highly doubt they would do that.
ETA: I think the reason for many players to wish for content that was already in previous games is that they liked this content and want it to be improved on now in TS4. That's just my guess, I feel the same about TS3 Into the Future, I hope the same or atleast a similar theme will be part of a future gp or ep, but I see that this pack for TS3 wasn't so popular, so I don't set my hopes too high.