Because the People Demand It [UPDATED-Tue 5/20 9AM]
A delegate projection update. Currently, it takes 2025 to win.

Current Pledged Delegate Count + Superdel. Endorsements
Obama: 1612.5 + 302.5 = 1915
Clinton: 1442.5 + 276.5 = 1719
Obama + 196

Upcoming Primary Projections (based on recent polls for KY, OR, SD, PR, worth a combined 388 delegates)
Obama: 77
Clinton: 96
Clinton +19

Total:
Obama 1992
Clinton 1815
Obama +177

What's left? 16 pledged delegates in Montana + 217 Superdelegates. Assuming he gets 8 in MT as he should, Obama would need only 25 of the remaining 217 superdelegates to reach 2025. That's 11.5%.

(Even if Florida and Michigan are added, with Obama receiving the 55 uncommitted delegates from MI, he would under this scenario need only 75 of the remaining 247 superdelegates. Hillary would need 193 of them.)

State projection details below:
KY (51): Clinton - 67.6 - 32.4 (34-17) C +17 [C +176k of 500k]
OR (52): Obama - 54.9 - 45.1 (29-23) O +6 [O +58.8k of 600k]
SD (15): Obama - 52.6 - 47.4 (8-7) O +1 [O +4.2k of 100k]
PR (55): Clinton - 58.7 - 41.3 (32-23) C +9 [C +156.6k of 900k]

Clinton gains 268,400 in the popular vote in these 4 contests, putting her about 328,000 behind Obama in the popular vote total of contested states where we have individual vote totals. If you add some reasonable estimates (by RealClearPolitics) of the caucus states that do not report individual vote totals this leaves her about 438,000 behind. Even adding Florida to this group will leave her 143,000 behind. That's out of more than 33 million votes. Pretty close, but Obama wins by any remotely fair count if these polls and turnout models hold up.