At a meeting hosted by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in Saudi Arabia, women attendees were told that they were required to wear abayas "due to the conservative nature of the Islamic religion." The UNESCO meeting, a forum of non-governmental organizations on the topic of "Youth and their Social Impact," was held in Riyadh, Saudi Arabia, on May 3-4, 2017.
In the words of the FAQs for the forum:
"CULTURAL AND LOCAL SPECIFICITIES
Due to the conservative nature of the Islamic religion and practice in Saudi Arabia, travelers are advised to observe the following dress code when in public places:
• Men should wear long pants and shirts not open above the collar bone. For business meetings, a conservative suit is expected.
• Women are expected to dress conservatively. It is required to wear an Abaya, which is a long robe, usually black, that cover most of their body. Make sure to select clothes that cover arms and shoulders, and opt for long trousers in place of shorts...
Meeting & Greeting
• Due to the conservative nature of the Saudi society, men and women are reserved in their interaction in public.
• It is uncommon for men to shake hands with women, unless women offer their hand first."