No. Your child does not intentionally mispronounce sounds. They have developed a speech pattern over time that is unconscious, but certainly within their control to change with instruction.
We don’t know why children develop different speech patterns. In many cases, the sounds are simply delayed in their acquisition, and with time will likely develop on their own. Providing families with suggestions to encourage the development of these sounds is often very helpful.
Other children’s speech patterns are much more complex and vary from a typical developmental pattern. These children usually require direct speech therapy. It may be that a similar speech pattern has occurred in the family, suggesting a hereditary link, or a hearing loss as early as 12 months due to recurrent ear infections can also affect sound acquisition. For many children, however, the cause is unknown. What we do know however, is that your child is not willingly trying to talk this way, it is simply the only way they know how to use their sounds!