White Balance

Two important facts apply here:

1. A Raw file is what its name implies; raw, unprocessed data from the sensor. The only operation that was done on it by the camera firmware was the digitizing of the sensor's analog output (voltages). A Raw doesn't even have color data, because sensor voltages are caused by the intensity of the light hitting it, not its color. The color is interpolated in by Lightroom along with a lot of other image adjustments, including WB. So when LR applies that processing it is the first time, like a flower being grown from virgin soil. A Jpg is the product of such processing, whether done by a Raw conversion application or by the camera firmware. The image data has been "baked in", it is a grown flower. You can do some tweaking - prune some branches, paint the petals with paint (a' la Alice in Wonderland), but you can't convincingly change a dandelion to a rose.

2. Nowadays cameras write Raw data with 14 bit precision, or at least 12 bits. LR does its calculations to 16 bit precision. Jpgs contain only 8 bit data. In the conversion to 8 bits a lot of the original data is lost to rounding off, like my telling you I have 5 dollars when I really have 542 cents. Also, Jpgs are always compressed files; the first thing any app does when opening them is to decompress it. In these two operations more data is lost. High bit depth and abundant data gives flexibility in processing Raws that Jpgs can't have.