When working with a JPEG file, Lightroom only displays "As Shot", "Auto", and "Custom" in this pull-down menu.
You can, however, adjust white balance using the "temp" and "tint" sliders.

If you want the presets that are available with RAW files (I do) it is possible and not all that difficult.
Start by working with a RAW file in the Develop Module and set white balance to "Daylight" in the Basic Panel.

Then on the left side of the screen create a new preset named "Daylight" copying only the White Balance settings.

Do this for all of the usual WB settings, adding Cloudy, Shade, Tungsten, Flourscent, and Flash.
Finally create a new preset folder named "White Balance Settings" and move your new presets into it.

Now you will have all the white balance presets to use with JPEGs that were previously available only for RAW files.

Mandrake