I think at the moment it's the opposite: It seems based on how many celebrities talk. When we watch them on TV, youtube, tiktok whatever they're not real people but just playing a role. It's not how they really are in their real life. The overacted enthusiasm is like a marketing tool.

As people tend to look up at celebrities and admire them they start associating this with good things and I think this is why they adopted such styles for chatbots.