Is it considered as normal behaviour to simply break off contact and no longer be reachable?

Apart from the „what's neurotypical behaviour vs. whats autistic behaviour“ thing: I am interested in the cause that people suddenly stop contact. Why is that? I see it a lot: Everything seems to be fine and then suddenly: they are no longer available. 

Let me give you some examples:

I get help from a social service where a social worker comes to my house to help me with things like driving to the car wash, looking for a smaller apartment for me and my elderly mother, making phone calls. Four of these women who used to help me just stopped coming without explanation and did not respond to my emails. I had to contact their boss and demand that they send me another person. I even switched to another provider, but it was the same there: they ghosted me after a few meetings. 

Another example: because I am afraid of driving in heavy traffic, I contacted my former driving instructor, with whom I always got along quite well. He was very nice and we had, I think, 6 or 7 lessons and planned to do some highway driving. Then I was in the hospital for a week and texted him that I would be home on June 15th. He wished me well and when I got home from the hospital I ran into him at the mall. We said we would text the next week. It was always he who contacted me because he is very busy and he had to squeeze me in. This time he never got back to me. I am afraid that I have done something wrong. I feel like the annoying teenager I was when I took my first driving lesson, and now I'm imagining him thinking, "Oh, please, not her again. She’s so burdensome. I’ll just ghost her" 

And speaking of the phenomenon in my family, my sisters just reduced their contact with me to a minimum. Nothing bad happened, but I think they can't stand the fact that I have to take care of my mother, who is disabled. They say I should have my own life, just like them, and I would either have to be loyal to my mother or to them, I would have to choose. I didn't even understand what they meant. My mother needs me and they have never been able to afford to help when things got difficult. They have their own life (no children but lots of hobbies) and I'm boring or what? 

I could give you more examples (there was the doctor who just disappeared and left me without care, or the woman I considered a friend who started canceling our meetings at the last moment every time), but I don't want to bore you with my sad stories. 

I just don't understand what to make of it. Am I just something to throw away when other things are more interesting? 

Believe me: I’m not the kind of person who gets on people's nerves by constantly texting or calling or begging for dates. 

I was taught from an early age not to be annoying and that people have their own lives that I have to respect. I am never part of that life. Is that the problem? Do I have to text and call and beg because people want to be seen and adored and they want to feel like heroes? But that's not my approach. That's not how I deal with relationships. 

I'm just nice and friendly (at least I try), listen to them (people tend to tell me everything, maybe that's a problem too?) but I need a lot of space. I need a lot of quiet time. Structure. I am not a party person. So I cannot be around people constantly.

I always try not to talk about my special interests when I’m with people and never be unempathetic. 

I ask myself, what's wrong? Other people have friends and family that care. I always try to do my best, but people tend to treat me like something unimportant, like a tissue that can be thrown away after use, even when I pay them to spend time with me like the women from the social service agency. 

Is it a sign of the times? Are we like this today? Is this normal? What do you think?