I figured this out from another site. Apple's so-called genius designers, developers of iOS 7, decided to make regular old SMS texts unavailable to iMessage (iPhone to iPhone) users if the receiving iPhone is unavailable at that moment to receive an iMessage, UNLESS you do the following ridiculous steps. You have to go to your Settings and TURN ON the option to allow SMS text messages. And THEN you have to choose "send as text message" when the iMessage fails. ARE YOU KIDDING me Apple? Are you monitoring this thread. That s*hit is crazy!
Apple, seriously: should people have to TURN ON a setting like this? Shouldn't the setting be ON as a default unless people go in and adjust it so they want to exclusively use iMessage? Do you seriously think that all iPhone users want to get message failures and then jump through a bunch of hoops to get their messages to go through. Is anyone in charge over there? And did it occur to you to make communicate about this to your loyal users, one of which I used to be.
There are so many riduculous new steps to go through to accomplish simple tasks in iOS 7 that were not a part of iOS 6. You've overcomplicated it. I have been defending iOS 7 a lot lately to doubters and haters: I'm done. I'm seriously considering finally making a change to Android, not because I love Android, but because I'm so frustrated with all the silly, little non-sensical moves like this you are making under the guise of "new and improved."