Marcus tended to have an acute awareness of his surroundings, for all that he tried to maintain a pretense of not giving a shit. It was important to know when an audience was around, and what type of audience it was. He wasn't unused to people turning around and leaving once they saw him, either. However, in this case he misinterpreted the the motive for the woman's exit and assumed he was using a piece of equipment that she preferred. Since most of his routine could be done without it, he abandoned the device. "Machine's all yours, chica. Don't gotta run away."
Maybe the universe would reward him for this sudden act of gallantry. He sure wouldn't say no to a nicely grilled piece of meat, or even just a decently spiced marinara. He found the food here incredibly bland, as a general rule. He even stacked the cards a little more in his favor, karma-wise, by wiping down the machine after getting up from it. It only took a second to do, and Marcus actually took gym etiquette fairly seriously.