I mean, it signals general trends of really poor social skills. Obviously, expecting workers to prostrate themselves upon the customer isn't going to happen. However, if this article is at all literal, it suggests workers aren't even acknowledging the customers at all. At the risk of sounding a lot bitchier than I hopefully am, I have had this happen to me, and my thoughts were "Are you stoned right now? Do I have your attention? How can I know you get my order right if you're not even going to show me you're not half-asleep on the job?" Even a singular half-assed "what can I get you" would dispel those worries and not even trying to socialize at all isn't going to help those much-needed skills.
It also signals to me that you're embracing the whole "I am a replaceable economic unit" mentality. I get that your average food service worker is dead inside but full-on viewing yourself as a mindless work drone is going to wreck your self-esteem and serves to perpetuate that kind of work culture. I can even imagine it to be a self-fulfilling prophecy. After all, you're showing as much emotion as a computer, if not less, so why not having one of them serve your function and lose nothing? Or, hell, why not Mr. Ethnic Diversity? He can work for cheaper and you clearly aren't enthusiastic about your job, so it's a "win-win"!