Your idea of practicing your brain while being high out of your mind and chilling on the couch is not very admirable. Also, selling cell phones is not rocket science. So, what other activities are we talking about here?
I do read, but it's not for the sake of practicing my brain, it's because I enjoy a good read. I read for the info. Actually, I think I read for several hours a day. I write a lot too.
And I would like to defend your cheap shot at my current profession (it's an electronics store, not a cell phone store by the way). I'm not some clerk, and I'm not some gives-a-fuck-about-his-job dude. I take pride in my work because I am very good at what I do. I am a very good customer service provider. I have very very satisfied customers. I am committed to my work. Maybe you haven't shared any of these things with me, work-wise, and your spectrum is narrower. Maybe not, but I'll tell you a few things about my job. Our cash/credit orders system (which we also use to order products from our distributors, handle service jobs from beginning to end, basically, it's the same system that anyone that works for the chain uses, even the top bosses, the logistics department, the economy department, etc) is one of the most complex ones in all of the businesses in this country. Knowing the ins and outs is actually comparable to rocket science since you wanted to try and be funny, so fuck you.

I don't just sell, I take care of all the day-to-day things that are involved with running a big store that covers private customers as well as business customers. All our employees do. Also, as a seller you are basically manipulating people into thinking they are making the choices themselves. You are using mental illusions and that kinda stuff when you make a sale. I don't just point a customer to the phones and take money when they decide what they want to get. Selling is a science in its own right because there is so much stuff you can do. I get free courses sponsored by my employer every month or so.
And I think it's a common misconception that I smoke a lot more than I do.