This is what Theopedia states:
Premillennialists fall into two primary categories: historic premillennialism and dispensational premillennialism. Historic premillennialism is so called because it is the classic form which may be found in writings of some of the early church fathers (mentioned above), although in an undeveloped form. Dispensational premillennialism is that form which derives from John Nelson Darby (1800-1882) and dispensational theology. It is dispensational premillenialism that first taught the notion of a pre-tribulation rapture.
Historic premillennialists reject the idea of a pre-tribulation rapture and the uniquely Jewish nature of the dispensationalist's millennial kingdom (see below). It is often assumed that all premillennialists are dispensational in their theology. This is a confusion that should be avoided. Historic premillennialists such as George Eldon Ladd are consistent Calvinists who did not accept the basic tenets of dispensationalism.
I take it then that the defense of a erroneous doctrine (amillennialism), which appeared 200 years or so after the end of the Apostolic Era, is to try and discredit a doctrine that was believed during the Apostolic Era (premillennialism). Eschatology is an area where the Reformers are not so far removed from their former oppressor. I think this is also one of the principal reasons the Reformed churches are in a death spiral.
The eschatology the Reformed embrace requires allegorical interpretation and spiritizing prophecy. As previous articles so aptly pointed out this approach to understanding Scripture, rather than literal interpretation, makes it easy to ignore clear doctrine in other areas.