I can read and catch up on many group text messages very quickly but having to go through dozens of voice messages sounds much more time consuming, even if you can choose faster speeds.
Plus, unless you're a superb on the spot thinker or on a rip that day, it can be hard to express longer thoughts in one shot and having to rerecord is also not appealing. With text, you can edit it easily.
You might find the research about sensory processing sensitivity interesting.
"Theory and research suggest that sensory processing sensitivity (SPS), found in roughly 20% of humans and over 100 other species, is a trait associated with greater sensitivity and responsiveness to the environment and to social stimuli. Self-report studies have shown that high-SPS individuals are strongly affected by others' moods, but no previous study has examined neural systems engaged in response to others' emotions."
Plus, unless you're a superb on the spot thinker or on a rip that day, it can be hard to express longer thoughts in one shot and having to rerecord is also not appealing. With text, you can edit it easily.