Click on "OPEN PETITIONS" above, and you'll see that the 3 current options (All Petitions, Trending, and Popular) display only the titles and signature totals of petitions. This makes it impossible to quickly determine how much time each petition has left to acquire 25,000 signatures. And because the promise to answer each one that reaches that threshold within 30 days is the major attraction of this site, expiration dates are a key factor in determining if any petitions merit our serious consideration.
For example, most of us probably wouldn't take the time to research an issue we are unfamiliar with if the petition addressing it only had 200 signatures and would expire the next day. However, we might if it still had 29 days to go, or only needed a few more signatures to reach 25,000!