I just don't understand

As stated there is no one correct conversion.  RAW lets you choose from nearly infinite possibilities.

One part of the RAW to JPEG conversion is setting the white balance.  The color of your light source will actually change how you process the RAW data, you usually want to remove those color shifts from the final image, but the camera can have a hard time figuring out exactly what these are.

If you have a bunch of fall leaves in your image, your camera might think it is a color cast from a light source, and actually try to remove the color of the foliage giving you a blue or purple tint.

Once the conversion from RAW to JPEG has been done with a specific white balance, you can't undo this given just the JPEG.  You can adjust it slightly, but the further you try to shift the white balance in the JPEG the worse it will start to look.

Many people swear by "Brand X has better colors than Brand Y", but what they are really saying is they prefer Brand X's decisions in the RAW to JPEG conversion process.  Often it is what they are used to.

A typical consumer camera will tend to over saturated colors and over-sharpened images, since that is what consumers like to see.

Another factor is number of data bits.  Most RAW files are 12 to 14 bits, which represent how many distinct levels can be captured.  JPEG is 8 bits, but most displays are only 6 or 7 bits.  Each bit doubles how many values can be stored.  So 6 bits is 64 values, 7 bits is 128, 8 bits is 256, 12 bits is 4096 values, etc.

All this means is that you have more room to work with your image from the RAW.  The tradeoff is it takes a lot more space and you have processing time going from RAW to JPEG.   I work in RAW so I can get my white balance correct after the fact and have more room to process the files before converting to JPEG.

Most cameras let you adjust JPEG parameters to let you get closer to what you desire.  If you can get what you want out of camera with a JPEG there is no need to shoot RAW.

Eric