It seems to me that you have either misread or misinterpreted something in your reading. Lightroom and Camera Raw come with default settings. Those default settings may not be right for your situation, so you have the opportunity to change those settings to what ever you need. If you want to, you can even change the default settings so that they include the adjustments that you have made.
The sharpening adjustments that you make in Camera Raw or Lightroom should be included in any images that you finish in Photoshop or export from Lightroom. At least that is how it works for me.
I read that the default was preview only and they said it should be changed to for all images. Now, I went back and looked carefuly at the images I had processed. Indeed, the sharpening was not applied and all that time was wasted! I now have to go back again and reprocess most of the files.
All is not lost. The sharpening settings that you so laborously made are stored in the sidecar (*.xmp) files or the central database, depending on your preferences. All you have to do is to turn on apply sharpening to all images.This setting is "sticky" and you can then open and save the raw files as JPEGs or TIFFs, overwriting the unhsarpened ones. To automate the process you can write a simple action to do this. Actions are covered in the Real World Camera Raw book.
Anyway, WHY did they make it as a default? I bet many people had processed many files before realizing that the sharpening changes were not saved.
They didn't...somehow, you changed the default preferences yourself. Since Camera Raw 4, the "default" settings in the Camera Raw preferences have been set to sharpen the images...(previously, I believe the default was set to sharpen the previews only). So, the only thing you've lost is the sharpening in your rendered tiffs or jpegs. The sharpening settings are still there in the raw file xmp settings. As indicated previously, you'll simply need to go back to the original raw files and re-process. Assuming you haven't done a tone of work on the images in Photoshop after opening them from Camera Raw, you can re-process them. It'll take some machine time but if you either batch process directly from Camera Raw, or via a Photoshop Batch process using actions or even Image Processor from Bridge you can end up with properly processed files.