@Terrificli -- Things are not always that easy. There are a number of reasons someone could have all of their investments wrapped up in one stock. Perhaps they work for a company that gives stock as incentives to employees. Perhaps they want to support a local company that provides a lot of jobs to friends and neighbors. Perhaps they are in the upper management of a company that awards stock to executives.
In any of those cases, buying stock in another company might be considered disloyal. The risk associated with not diversifying might be considered slight to the ostracism an investor might otherwise face.