Two things;
1) Extroverts don't understand that it's an actual thing that people like to be by themselves (not as a rule, but I've sure had that discussion every once in a while), whereas I've never met an introvert who didn't understand that some people like to be around others, and in fact prefer it to being alone.
2) I don't think this topic has ever been about a deeper understanding of the motivations and hopes of others, simply an understanding that they like different stuff from what you like and there's nothing wrong with them for it.
I've talked to all sorts of people. A few things stands out.
One of them is that almost all people believe that when a relationship is over, one needs time to recharge, before going into a new relationship.
Some people seem to bound from relationship to relationship, without ever being by themselves. These people cannot stand to be by themselves. If their S/O is out, they HAVE to be with people, even if it means they are hanging around with people who just want to screw them, even if that means screwing up their relationship. Such people are considered highly dysfunctional.
This fact, that almost all people consider that if you can't be alone, or just even avoid being alone when it is reasonable to do so, makes one highly dysfunctional, means that almost everyone accepts that it is perfectly fine to be by oneself some of the time.
It is also accepted by almost all people, that one of the worst things one can ever do to a criminal in prison, is to put them into solitary confinement, because everyone, including almost all introverts, needs company sometime.
This idea of "extroverts don't understand me", usually amounts to something like this:
Extrovert: We're all going to your best friend's birthday party.
Introvert: Fine.
Extrovert. It's your
best friend's birthday party. Aren't you coming?
Introvert: Why?
Extrovert. Because it's your
best friend's birthday party.
Introvert: So?
Extrovert: Don't you want to have friends?
Introvert: Why?
At the party:
Best friend: Where's introvert?
Extrovert: He said he wasn't coming.
Best friend: I can't believe that selfish git. After all the times I helped him out, he couldn't be asked to turn up. I never expected him to stay. I just wanted to see him for 5 minutes on my birthday. Is that so much to ask?
15 Introverts: No. It's what is called being reasonable. He's just a dick.
After the party:
Extrovert: Hey. It was a great party. Everyone thinks you're a dick.
Introvert: What on Earth did I do wrong? Just because I don't want to hang with the crowd all night, talking about nothing?
Extrovert thinking: (No point explaining. If he can't see why he's a dick, he never will).