1 They hate hearing their voice
Many people don't like hearing their own voice, as it sounds different. People don't feel comfortable listening to themselves and so they prefer to text.
2 They feel embarrassed
Some people feel embarrassed to leave a voice message that people can listen to anytime. Those people prefer to text in order to feel more comfortable.
3 They can't listen in public
Many people don't like to send voice messages in order not to get voice replies. Many people hate getting voice replies because they are not always able to hear them in public.
4 Privacy concerns
Some people don't like to send voice messages for privacy concerns. Those people fear that their messages might be used against them if the wrong person accessed the phone. (See Why Do People Care About Online Privacy?)
5 They don't want to spend time listenting
Some people don't like voice messages because they don't like to spend time listening to them. Those people prefer sending and receiving texts because they consider them faster.
6 They are too shy
Shy people might feel very embarrassed to use voice messages. Many shy people will prefer texting over voice messages when given both options.
7 They don't consider it practical
Many people don't consider voice messages a practical way of communication and they prefer a faster and more practical method to deliver the message.
8 They are forced to listen
Because a person can't know what a voice message is about before listening to it, some people feel obligated to listen to voice messages when they get them.
9 They are introverts
Introverts are more likely to prefer texting than sending voice messages. Extroverts, on the other hand, might feel comfortable using both text and voice messages. (See The body language of introverts)