I think this is because it's such a good reward. Everybody has to pay their dues at the start; for me, that's part of the fun. It stinks that I wasn't able to complete my first several time-limited goals, but failing has taught me to save up certain items in anticipation for the next one. I've always been an impatient person, and I actually think this genre has taught me more patience in general: waiting for things to happen/refresh; waiting for rare items to show up; waiting for energy; waiting for inventory to build, etc. has made waiting easier for me. Every game of this genre I've played has been the same way.
As far as the Research Center goes, it's a long-term goal. This is my second monster hunt season, and I have 27 tokens. It'll take probably a couple more seasons to get to 70. That's okay. I'm enjoying seeing my neighbors who've been playing for years being able to get it now.
Edited to add: I have not heard any of my neighbors complain of the game being too easy, and some have been playing since the start.