Because it's Wrestlemania. They won't book a Face vs Face title match! It's nearly always Face vs Heel for the title (I don't recall any Face vs Face but I could be wrong) because it sells better. Punk won't turn heel for awhile since he's red hot on RAW. Sheamus is the same on Smackdown.
WM23 had Face vs. Face Title matches but yeah when you consider that Punk and Sheamus are not established headliners yet it would make more sense to pair them up with either a top face or a heel to protect them from the crowd.
I can see the WM card going like this
WHC: Sheamus vs. Orton - they have history, and they could make a story where Sheamus has never beaten Orton yet.
WWE Title: CM Punk vs. Triple H - this was rumored they can already use the story with Johnny Ace to build on this
Jericho vs. Undertaker - this could be the last chance to have Jericho and Undertaker face each other on PPV.
Then of course with Rock vs. Cena, you have a pretty sexy card.
As for the Rumble ... I have some Plus and minuses
What I didn't like:
Too many guest entrants, I counted 7/30, that almost 1/5th while I had fun seeing the Announcers an Foley (though they could have done something with him), Im surprised they could not fit in Cena, Kane, Henry, Ryder, McIntyre in the card.
A lot of dead time in the beginning. The Miz and Rhodes had to carry 2/3 of the Rumble.
What I liked:
Rhodes and The Miz being on the Rumble early and going coast to coast. Nice to see the WWE putting faith in Rhodes or The Miz carrying the whole thing.
Back to 30 ... 40 participants was just too much for me.
The ending ... Loved that they dedicated plenty of time with Sheamus and Jericho at the end. Last three rumbles have been lackluster here having quick eliminations when it went to the final two. For this year it was nice having the last two going at it for a long period. Adding a climatic finish to the Rumble.