Two potential problems:

1) I don't recall who it is, but someone who is not google holds a patent (sigh) on using the URL path after the host as the search string.

2) If it was my property to control, I would not want google.com/{*} to accumulate links on the internet. That is to say, before there was google.com/maps, one would expect some people to link to that URL directing their users to search for maps. Now that google is so big, that could be a dicey prospect, because substituting their own property for what would have previously been a search could reasonably be seen as anti-competitive.