Because TBS games are few and far between. Years between good ones sometimes. With the economy the way it is, and two TBS comming out so close together, people are going to chose one or the other. There's a reason there's a "5" in Civ 5, and I think I, and many others were hoping EwoM would hit one out of the park and give Civ5 an "underdog punch".
In my case, my friends and I were chosing which one to ALL get together, so we could all play together (we don't have 2 X $250 to waist). I was really, REALLY hoping for them to get EwoM, but in the state it was released in, I had no chance in heck to get them to get it with me. Even as I had them over, and started demoing the game, I had to tell them it not released with MP, and even when/if MP starts, there will not even be strategic battles (and we buy TBS games for the "S"). That got them furrowing their brows from the start.
Not to mention, as I tried my best to demo it in front of all of them, I could not figure out or find most the rules/UI info I needed to play the game for them . They kept asking all sorts of questions about the rules; I could not answer them; we could find nothing in the rule"pamphlet" or in the tooltips. And then the bugs kept kicking in all over the place (When the game would lock up, we would reload, only to see our 8-group units down to 4 or less). Over the hours of play, I watched in vain as their faces slowly shlumped into scowls.
Nope, unless SD pulls a hail-Marry pass before Civ5 comes out, my friends will all be getting Civ5. Darn. Sad. But who knows, maybe by Christmas EwoM will be "Christmas present worthy".