I'm not familiar with the world of high-powered international conferences, but I wonder if it might have something to do with the subject matter and the type of people attending.
If the event brings together, for example, people who work mainly in church-related or nonprofit groups, NGOs, aid organizations, development, refugees, climate, education, health care, etc., then it may self-select for idealistic or optimistic personality types who feel that the cause itself is inherently inspiring, or that they need continuing inspiration to do their work; and/or teaching / caring / nurturing professions who are used to trying to encourage others, to find something positive to say about everyone.
Or if it's a group of management or business types, it may be typical to praise and flatter everyone they meet, in case they might later be useful as a networking contact.
I'll go out on a limb and venture to guess that it was probably not a group of engineers and scientists. (-: