I would say they could put past event items in there and make everyone happy but then what would they put on the cash shop.

Although if they really thought about it they could do it just over a month before a new patch and force ppl to pay an extra month's sub if they want the items but do not want to use the cash shop and probably make more money. Then throw a few extras in there like a few mounts they could just rotate thru so you only see them about once a year to attract even more. If the log in campaign lasts 2 weeks, require say 10-11 log ins out of 14 for the mount and/or cash shop item(s).

And if you cannot be bothered to take 2 minutes to log in on 10 random days in 2 week period, then maybe that mount wasn't as important to you as you thought.