Why would Asus encrypt the C partition?

I bought an Asus Asus X205TA, 11.6" Laptop on which Asus encrypted the C partition. This is quite annoying because you can do nothing to the C partition - no images, no recimg and even AOMEI OneKey did not work. For my wife we bought an Asus 10" T100 Transformer. Luckily that was not encrypted. Since the wife was so pleased with the T100, she recommended it to a friend who bought it too. And guess what, on that one the C partition was also encrypted. I talked to the second level support at Asus and they were also speechless. For my X205 they granted an RMA for it to be fixed at their service center in Cal. For the friends T100 we still have to negotiate. I wonder what interest Asus has to bitlocker encrypt the C partition. And also I thought that bitlocker would only work with 8.1 Pro - but those devices run on an 8.1 vanilla 32bit.