gdalbuildvrt strips attribute table

I would like to create a virtual raster from an .img file that has associated .ige, .rde, .rrd, and .xml files. I am doing this to enable virtual I/O so I want an "exact copy" of the original raster.

I am just calling this from the command line:

gdalbuildvrt file.vrt file.img

This creates a VRT but the attribute table is stripped; instead of categorical data I now have continuous values. How can I fix this?