Aside from doing multiple things all at once to maximize pleasure, multitasking is not the go to strategy to maximize performance or productivity.

The main reason people might feel a proclivity towards multitasking is the fact that they might be under extreme time pressure, where they feel they will definitely fall far behind at some point in the future, no matter what they do, or at least if they kept going at the same pace as everybody else who is not under the same or a greater amount of stress or time pressure than theirs, or if they tried to handle things one task or thing at a time. It’s not that they think that they’ll get more things done if they multitask. But rather, they multitask, because they think or feel that they can’t get anything done, no matter what they do. At least not on time. They can finish everything on their plate if they went about it normally, one thing at a time, but they will finish everything way after they have to or want to. No matter what they do, they feel they will be too late. It’s a stress response, something that comes from being under too much time pressure, not a strategy they pick, because they believe it will help them get things done more or better, or get more done in less time. 

Also many people use multitasking as a mechanism for shielding themselves from outside intrusion or attacks, if they are stuck with people who have no respect for boundaries or other people’s feelings. If you are doing a lot of stuff simultaneously, you can easily deflect any attacks on you by simply saying that you’re busy. Can’t you see I’m busy? It was so obvious, you really didn’t need to verbally clarify that. That will save you a lot of effort, because defending yourself from such attacks when you don’t look so occupied will be almost always impossible. Instead of not responding for example because you don’t want to, you simply have to look busy, where the explanation for why you’re not responding is supposed to be obvious for anyone who’s judging the situation from outside, even if the real reason behind you not responding is the fact that you don’t want to at this moment, you’re not in the right mood or state to give a response that is not offensive or will drain your energy or make you feel worse afterwards, even if there’s nothing wrong with the person who wants to speak with you at the moment, or with what they have to say, or you’re simply under huge stress or too tired and can’t handle anything else at the moment, or because you’re simply under attack by a toxic or abusive person, and you don’t want to ever respond or engage with such person, or you don’t want to be interrupted at the moment for any reason and you need to hyper focus. Because after all, if it were somebody else who you really have no problem with responding to them, you’d happily respond and then go back to whatever you’re doing without experiencing any pain in the process.

People who can’t get space to do what they really want unchecked and uninterrupted all they want usually resort to multitasking as a last ditch effort to still get some space despite not being able to get actual physical space all for themselves away from people, to do or be what they want, all they want the way they want it, for as long as they want it. In other words, they’re stuck, and they currently still have no way out. They don’t do it because they’re in love with multitasking. They need space, and they’re still not able to get that space.

Stop telling people that they should stop trying to multitask because the human brain can’t do multiple things at once simultaneously with full focus. They know that. They just don’t have the opportunity, the luxury, or the right environment, circumstances, or living conditions, that can enable them to no longer have a reason to or no option but to multitask. Either give them that, or shut up.