Most Helpful Guy
It's unfortunate but that is how a lot of people now a days just get rid of someone who they never were really serious about in the first place. It says more about the ghoster than the one being ghosted though. So I wouldn't let it get to you. High quality people in your life would want to be around you and respect you for who you are.
Most Helpful Girl
I believe it's because they just simply couldn't care less, and to them it's easier than having to deal with the girl if they are upset/hurt/continually messaging for answers etc.
however, I do not agree and think honesty helps everyone. Feedback is vital for growth and learning and I would always rather know why they are no longer interested so I can then use that moving forward.