Reddit definitely makes use of it's CDN and caching for logged out users. Since they make up the significant proportion (exact statistics escape me) of visitor

Reddit definitely makes use of it's CDN and caching for logged out users. Since they make up the significant proportion (exact statistics escape me) of visitors, it's not surprising that's where their effort has been directed. In contrast, every page load by a logged-in user requires unique database queries for things like vote status on submissions and comments.