Our church switched to the ESV nearly six years ago when our pastor was first hired. Up to that point, we used the NASB.
Why the switch? I don't know. Pastor's preference?
I don't like the ESV as well as I like the NASB, but I can't complain too much about it. The ESV doesn't always use the best translation of a word or phrase, in my opinion, and sometimes that misses the meaning of the passage. But not seriously, and not often enough I mind that much. I still use my NASB, and read the passages in both adult Bible study and in church from that.
As someone has said, I don't mind the NIV, but it isn't as good a translation, given it is a dynamic (thought-for-thought) translation vs. the literal word-for-word, or in some cases, by necessity, phrase for word translation, of both the ESV and the NASB. For that reason, I can see a church making that change. I am more for a literal interpretation than any other.