I just started to use a smart phone last year. Before that, my clients were asking for responsive websites. Well, they did not know the term "responsive", but they want their websites to show nicely on mobile phone, and they always use their phone to check their websites and other sites too. I understood that's the market's need, and hence I have to make the website responsive.
Ever since I started to use my smart phone to browse the websites, I found that it's very important to have a responsive website, even email. Though I still use my computer to go online often, sometimes I do check on some sites with my phone. I really appreciate those website owners to take the effort to make their sites and also the newsletters responsive, otherwise I would not be able to browse their sites or read the newsletters using my phone, and perhaps I will just ignore these sites. Moreover, I think those who take the business seriously should really consider making their sites and newsletters responsive.
I think you would also prefer to browse a site with your phone comfortably, rather than looking at the small fonts or some sections have been cut off. It's the trend now, as more people are using smart phone to surf net.