When we talk about working smart there are actually different categories to this and they are jobs that everyone can do, there are lots of freelance jobs that even people that are poor, average and in the middle class can do comfortably from the comfort of their homes, in that case you cannot really say smart work is not for everyone because there are ways to work smartly as someone that's coming up or building from scratch that can eventually be profitable in the long run, in a nutshell it all depends on the type of job.
it actually depends on a type of Job one is doing, working smartly is not only doing only jobs, being diligent and knowing your job description is also a smart work. In this era there's no job that doesn't require advancement, you have to train and improve in your area of specialition, or you lose your job. Things are evolving and you have to follow the trend or you miss out. Working smart is but doing too much Is an act of doing the extraordinary at your working place to increase productivity. In all you're doing, be at your best even when no one is around to monitor you.