One of the reasons for speaking text from a file was to support the reading of text files created by other software. It could be anything from current weather readings or sports scores to status output from some other sensing program.
The other reason was that some people wanted BVC to speak text that was either too long or too difficult to manually enter into "Speak a Custom Phrase" style setups.
One user, for instance, wanted BVC to speak a random Bible passage every morning, but the total number and length of the passages was too much for a "Custom Phrase". Now, the passages can be stored in separate text files and BVC can randomly choose a text file (passage) to speak.
I just write the tools, it's the user's imagination that brings them to life!