The reality was that before Microsoft unilaterally added the XMLHttpRequest object in the late 90s, there was not much you could do with JavaScript even if you wanted to do something. Couple that with the fact that js engines were slow, front-end (DOM) APIs were severely limited, and most people connected to the 'net' through telephone landlines on slow PCs (by modern standards) meant that it made far more sense to do purely server-side page rendering.