Can't figure out why the show ended

Well ratings seem to help with the money thing. Also hour long ensembles are expensive. If you look at the season three cast, there's at least ten featured members. Add to that that ABC kept moving it around and that a show with a moving timeslot can't keep a fan base consistent then those are some reason why the show was cancelled.

By season four most of the S3 cast was gone and now you have to establish new characters and since there was a writers strike a lot of things just got jumbled and had to be cleaned up quickly. One last thing, the show started reaching far left at least to me and other people. Believe what you want and fight for what you want, that's fine. But not everyone agrees with liberal ideals and some shows that deal with politics don't work leaving one way or the other. I thought it was a joke that they had to show Shirley voting for Obama. It has nothing to do with being a lawyer. The Alan Denny wedding though I thought was great and loved it. But those are what I think are the reasons it was cancelled.

Like Sweating101 points out, a major cause of the cancellation in addition to expenses was the constantly changing timeslots. And then of course, promotion. This is a good article about the ending of the series: http://www.post-gazette.com/ae/2008/12/07/Boston-Legal-s-Kelley-delive rs-parting-shots/stories/200812070246

I too wish it would've lasted at least another full season, maybe even two. Especially since it would be interesting to see how the show would address the continuation of Bush's policy by the Democrats.

Boston Legal is one of the greatest shows ever.