As mentioned by John Galt the EU passed legislation which requires companies to allow users control over cookies, as a result most websites ask users for permission to use cookies and most give the user the ability to enable/disable different categories of cookie. It seems some sites periodically re-ask this although I would not expect this to be more than once a month.
See - http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm
Arguably non-EU websites would not need to implement this if they have no EU users but as in reality the overwhelming majority of websites around the world might have at least one EU user at some point and many a lot more it has in effect been necessary for all websites around the world to implement this.
A whole bunch of websites however including Yahoo use the same mechanism for managing cookies using 'oath' this is what I regard as a particularly nasty one as it does not seem to give the user the ability to opt out of any of the cookies. Either you accept them all or you are blocked from accessing websites using this system. Bleh! See - https://policies.oath.com/us/en/oath/privacy/topics/cookies/index.html
Note: Whilst as a Brit I regard the EU with (how shall I put this) mixed emotions, arguably the EU legislation on cookies and data protection (GDPR) is positive and as a result is being adopted in the US and being considered as a template for similar US legislation. [Cough, Facebook, cough.]
