I don't think MAC is the default [1]:

the following operating systems use IPv6 privacy extensions BY DEFAULT:

    All versions of Windows after Windows XP
    All versions of Mac OS X from 10.7 onward
    All versions of iOS since iOS 4.3
    All versions of Android since 4.0 (ICS)
    Some versions of Linux (and for others it can be easily configured)

For routers, then I have no way to tell. But I would be surprised if stateless addressing wasn't the default on the vast majority of retail routers.

[1] https://www.internetsociety.org/blog/2014/12/ipv6-privacy-ad...