Every time your conversation partner has to guess or piece together the meaning of what you are saying, it might interrupt the conversational flow. They might ask you to repeat or for clarification. But they might also try to figure it out by themselves, while you continue talking. In any case, the conversation will be interrupted at some point.
Now, imagine you’re at a networking event (this can be business or personal related): You want to be remembered as a potential partner, employee or friend. Instead, people will spend time and patience on trying to understand you. On the other hand, if you have good pronunciation skills, you will be more confident and able to participate in conversations and debates in a much better way.