You're paying more and getting less, usually both in quality and quantity, I don't see any reason to be happy about it.
Why would news outlets go the extra mile and re-frame it as "Companies are reducing the size of unhealthy products while maintaining the same price and here's why that's a good thing..." unless they were in the pocket of these companies? That would be editorializing to me.
Not that I actually believe that Mars bar size had any meaningful effect, but your rhetorical question is nonsensical.