Technically a chainguard protects the entire length of the chain while a bashguard only protects the largest chainring. The likely reason you find a bashguard included with cheap bikes sold by mass merchandisers is avoiding lawsuits. It is one less reason to get sued if Johnny gashes his leg on a chainring. You can find bashguards sold on eBay, Amazon and at most large online bike shops. You need to know how many teeth are on the large chainring and what the distance between the bolts that hold the chainrings on (usually 130 mm for road bikes and 104 mm for many others). There is even a You Tube video on how to install a bashguard in case you are baffled. They cost as little as a few dollars for a plastic one to well over $50 for some branded versions. Take a look at eBay to see what I mean. Type "bike bashguard and chainguard" in the search box.