Why do girls suddenly stop talking/contacting guys?

I am not new to relationships or talking to girls. This is why I really don't understand my situation. The past three girls I have talked to have suddenly stopped talking to, and contacting me. I brushed the first one off, telling myself I wouldn't want to be involved with someone who would just stop talking to me and not contact me back. After the second of this happening I was kind of pissed, but brushed it off as well. The third time, and most recent, I am completely dumbfounded. I really don't understand why these girls suddenly stop talking and don't respond to my efforts to contact them. For instance, I had plans to go out with this one girl the other day. I waited a little bit to hear from her in the morning, then sent a text asking if we are going to get together later. I didn't get a response all day or night. The next afternoon I simply said "I was looking forward to hanging out with you yesterday, hope all is well. I thought I'd at least hear from you." I haven't heard from her since then, and it's been a almost a week. These situations have been wrecking my brain, so Reddit, I turn to you. I've talked to my friends about it, but they haven't really helped. You are my last hope to make sense out of these situations.

TL:DR - Past three girls talked to just stopped communicating with me, even after great dates.

Edit - So one reason is that they aren't into them. Are there any other reasons girls would suddenly stop talking to someone?