Girl's Behavior

Why do so many people think it's okay to ghost?

So I was going to take a female friend and her two kids out on my boat this weekend. Saturday was the only day she could go so I decided at the last minute to reschedule work and take them out instead. Work can wait for another day is my saying. So Friday afternoon she agrees to go around 930 or 10 on Saturday morning. So Saturday rolls around and I text good morning at 7am with no response then about 9am I call with no answer. So I'm like eh she's probably sleeping still so I go out and buy life jackets for her kids because they have to wear them. I get some drinks and fill the ice chest with ice. At this point it's like 11 and I'm pissed because I'm realizing she stood me up so I sent her a nasty text saying she could have at least said hey we can't go. She calls probably 10 minutes later while im on the phone and i didn't realize it until i hung up so i call back with no answer. So 5 o'clock rolls around and she finally calls back saying her kid was sick. Okay... why not tell me that first thing in the morning so I could have just went to work or did something else? This happens all the time to the point where I'm just not inviting anyone on the boat anymore. Opinions? And it's not just the boat it's everything.
Why do so many people think it's okay to ghost?
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