Depends on the standards committee - for things like 3G telephones you can't legally implement the standard without licensing the patent pool, although license terms have to be 'fair, reasonable and nondiscriminatory' [1]. Qualcomm make more money from their patents on 3G technology than they do from producing and selling hardware. Likewise, there are patents on MP3 and h.264

I've heard people joke that the aim of being on a standards committee is to get as much of your protected IP into the standard as possible :)

[1] https://en.wikipedia.org/wiki/Reasonable_and_non-discriminat...