Specifically, BS in Starcraft.
I'm a harasser. My friend is a macroer. She can manage the constant building of massive armies of doom (usually their own doom, judging from the casualty numbers). But me? I'm an asshole. I'm a manipulative, irritating, passive-aggressive, jackass who does not ever give you a break but you can't quite lash out at me because oh poor little me what did I ever do to you?
As a bad player, I am well aware of the concept of negative momentum. You're losing and off-balance, so you keep losing and stay off-balance. Economy wrecked? That means a slow recovery and reduced aggression. Economy threatened, but not actually damaged? Reduced aggression too, there's defense to do! And then the other side has the initiative. They can now choose where to attack. They can build anywhere they want, because you're holed up, waiting for the next attack. Meanwhile you cannot expand, because expansions are vulnerable, so you starve in a little hole, wondering if you can ever escape.
I've been on this side. It doesn't help that I'm often overly defensive, not expanding until I think I can fully defend, which is a ridiculous notion, since failure to expand means limited resources which make it harder to build up a force to defend with, meanwhile the lack of pressure means my enemy can build up more as well.
It's all about the mind games.
While my friend builds armies that knock at the front door, I'm somewhere else, killing workers, hitting expansions, knocking out a building here and there. I won't win the game. I can't. I'm not an existential threat. But I cannot be ignored either. "Pay attention to me!"
It's trolling without words.
My reapers blow up a bunch of workers and sure, it hurts, it's an economic setback, but it's hardly a death blow. Well, unless your attack gets delayed by the need to defend. Unless you get nervous and have to keep more units back to defend against this. But which angle? Better cover them all. Now you're not attacking, but defending, but defending what? I dare you to leave and you don't dare to. This is what happens when facing bad players. They get totally paralyzed. I tell them sit and stay and they sit and stay, while my friend walks up with a hammer. They see her coming but they obediently sit and stay and wait.
Somewhere in there I transition to banshees, pretty much directly after, possibly taking the tech labs and abandoning the reaper tactics entirely. They're really just a filler until I can get the more flexible banshees.
Better players fare, well, better. They might not hide quite so much. But they aren't immune. Gotta deal with the harassment. Better leave a few units back. Maybe too many. Better build a few more anti-air. Maybe too many. Better get more detectors. Maybe too many. But never quite enough. But cannot not build them.
In this latter scenario my harassment isn't physical, but mental. I'm effectively neutralized as a threat. In one particular game I was almost certain that at any moment I'd get rolled over by one serious attack, but I kept the banshees out there and visible in a false show of strength. I still cannot be ignored. So my enemy tweaks his unit mixes, changes the build slightly, isn't quite comfortable. Or fully effective. Too much anti-air is trouble when a ground army rolls in. That ground army was my friend's, terribly expensive and easily lost, but with momentum, and expansions, who cares about lost resources? A 2-1 loss ratio means nothing if the resource income is 3-1, or more.
It isn't even necessary to attack a player to influence them. They can see what happens to their ally. They react to what didn't happen to them, but could.
I've pushed protoss into spamming stalkers or photon cannons. Depleting resources, hundreds or thousands, merely to deal with a few hundred worth of banshees. Missile turrets spammed. One zerg player rushed for hydralisks before realizing that it would be siege tanks, not banshees, that would ultimately destroy him, and of those I had no shortage (at least as far as he could tell!), so he quit.
It's a bit like the adage of how we always prepare to fight the previous war. I'm the first attack and very visible. So enemies prepare for that. Meanwhile my ally is barely noticeable, might as well not exist at all, until they show up with tomorrow's war.
It was a good day. I wonder what the next day, back to a comfortable losing streak, will be like. Win, lose, still pretty damn fun.