If you want to have an audio version that you can send just because it's easier to "hear" what you said instead of reading it, that's one thing. On the other hand, the other--and more common in my opinion--reason for a voice message is you want some way to store something ASAP without much distraction. For example while driving. A lot of phones have a voice memo button that you just hold down for 2 seconds, say whatever it is, and done. If I have to type it out to get it converted to audio, it seems redundant since the notes app on the iphone does the job usually for stuff like that. The voicemail hack is a lot more distraction less as typing on the iphone while driving is especially hazardous (a drawback to the tactile-less keyboard)

I guess it would have helped to check jott out first. The way you replied it sounded like jott was a text-to-speech service, not speech-to-text (which makes a lot more sense)