During the investigation done for MGNLUI-4126, mgeljic and I both arrived to the conclusion that the 'Pragma: no-cache' header is obsolete. It was meant for HTTP 1.0 which has been updated to 1.1 a long, long time ago. See for instance:

"I encountered an old smartphone browser that didn't support it [HTTP 1.1] about 9 years ago, but that's the last example I can think of where I'd even heard of an HTTP client that didn't."
Source: http://stackoverflow.com/questions/535053/which-webbrowsers-use-http-1-1-by-default (2009)

It is also unclear what the header was ever meant for. It would therefore make sense to try to remove it, in order to hopefully avoid more IE / legacy-software issues like the one I mentioned above.