Titanium white is not simply "a white", but rather "the white". The majority of white products used in everyday life use this particular shade. These common products include paper, plastics, tablets, and even toothpastes. Today's market uses this color because of it's excellent coverage / opacity and low chemical interaction. Furthermore, this color is known for prohibiting UV, which greatly enhances a paintings light fastness. A number of painters have named this particular color as "the perfect white".
Having this particular paint in a set of tools presents two attractive options. Mistakes can be quickly fixed using titanium white. Another option is as a base to mix the exact contrast required. Since contrast tweaking is so common among artists, painters often stock large amounts of this particular shade of white.