Because the program can't guess what you want.
Google (and countless others) can read perfectly well a
simple language query. If I search for "run", it returns all the "run"s it can find, but it's smart enough not to bring "Drunkard" or "Burundi". And with no need for hats, t's or pants. Only quotes, if I want them.
I would have liked it if it could have been as simple as that in MC. We're not in the 80s, when every utility had its own little dialect. And the argument about smartlists etc is understandable, but I suppose MC could have had a better search mode, while retaining the syntax to be used "under the hood".
In case anyone cares about a different point of view, plain users, not being programmers, may admire MC's magic but in the end they don't really care about or want to know how it performs it. I think MC is an amazing program to still have such shortcomings and from my little experience I'm convinced it's losing customers (albeit not me) because of this stress on a "do it yourself" attitude. If I had a say in it, I'd have all those wonderful tips, expressions, views etc that are lost somewhere in the forum gathered, updated and offered ready for use - perhaps tucked in advanced tabs or submenus so as to not intimidate newcomers. Or at least some examples, to facilitate learning, like in the Smartlists section...