http://www.pcworld.com/article/3098570/chromebooks/chromebook-shipments-are-exploding-but-not-replacing-windows-pcs.htmlChromebook shipment growth will be in the double digits this year, but the devices are not being used as Windows PC replacements, which is what Google had hoped for.Had Google hoped that Chromebooks wouldn't be used as PC replacements? Obviously not, and the use of the conjunction
but helps understand the intended meaning correctly.
CB