The use of disposable bibs for adults are most commonly seen within hospitals and dentists, you likely have seen and had one on you during your visits to the dentist. The purpose is simple, preventing a patient from getting stains and getting their clothes wet which otherwise would happen a lot during dentist visits. It's an effective way of improving hygiene through simple means and keep all parties involved satisfied during any procedure. That they're disposable helps save up time by skipping requiring washing the bibs. Generally you will not just see disposable adult bibs but plenty of other disposable items as well that helps keep up a good level of hygiene that is required in environments such as hospitals. But even if they are meant to be thrown away, these items do need to hold up a high quality, especially with absorption and durability as to avoid any accidental spill and stain that happens due to the lack of quality.
Commonly used products
Outside of disposable adult bibs there's aprons, wash gloves, laminates and protective sheets are all commonly used as disposable hygiene products. You might see some of these used for private use, but generally it will be mainly used within clinics and some items may be used in some industries or in elderly homes. Often these things will be acquired from a manufacturer they trust, such as Finess Hygiene whom focus on disposable hygiene products for hospitals as well as elderly homes to assists doctors and caretakers.