This is the first reference to "churches" since the letters to the churches at the beginning of the book (Revelation 3:22). This is undoubtedly because there will be no true churches in the world during the events of the tribulation period (Revelation 4-19). However, everything in the book is intended for the instruction of the churches in this present age.

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8