They should be worrying about people losing the habit of playing.
If, like me, you like your town, you're level 939, have maxed out the in-game cash, and nearly at the item limit, there's less and less incentive to play. No new items, no desire to move it all around, no new tasks. Just the daily thing for donuts you don't need because of everything already mentioned.
If you're a new player, you have all this to look forward to, and if they let people play past events again you're set for a while.
I spend 5 mins a day collecting income and playing the daily tasks, but only out of habit. Once that goes away, and there's nothing new to do, then what's the point. Take a photo of the town, save it somewhere, and look back fondly at something I used to enjoy before the creators stopped updating it.
But, with all that said, I am expecting something new soon...
