The tendency to mistake the superficial excitement derived from receiving text messages for the excitement bourne out of genuine chemistry between you and your text-happy new friend, especially prevalent in the budding stages of romance when a high degree of unfamiliarity is present between said parties. In the alternate context of an in-person or phone conversation, the same conversation would not be nearly as exciting.
It's no wonder your romances always crash so hard after you finally get to know the person, all the excitement between you is nothing more than the anticipation and reception of text messages. It's classic Con-Textual Attribution Error. Similar to the excitement and subsequent letdown of Christmas.