The well-intentioned social terrorist does not alert you before they invade your safety bubble. It's always a surprise. You'll come home, exhausted and eager to finally feel safe from unwanted interaction.
But then...
You're cornered like an animal. There's nowhere to go.
You'd always assumed that your own home was a safe place - a place where you were not in danger of sudden, undesired social interaction. But your pathetic delusions of safety implode into the realization that nowhere is safe anymore.
You could tell them no, but you aren't busy and you don't have any immediate plans, so you don't really have an acceptable reason to decline their company.
You could try to lie and say that you're just coming home to drop some stuff off before you have go somewhere. But if you do that, you'll have to spend the rest of the night in total darkness, because if your friend walks by and notices that your lights are on, they're going to know you were lying.
But if you allow this person into your house, you are no longer in control of when the interaction ends. This is not as simple as finding the right opportunity to walk away. No. This is some next-level crap. You can't just walk out of your own house and leave the person there. Where would you go?
If you want to be left alone, you're going to have to wait it out until you can convince the other person to leave.
But even then, it isn't over.
Now that you are aware that your home is not the impenetrable fortress of protection you once thought it was, you are forced to live in a constant state of slight uneasiness. Someone could surprise you at any time. What if your friend decides to surprise you with a visit every day? Now you have to worry about keeping your place picked up, "just in case." You're scared to play music or watch movies because then you can't pretend to not be home if someone knocks on your door.
You are no longer in control of your life.