I could imagine that blocking bot traffic, would improve their retargeting and make sure that the retargeting budget is spent on real people leading to an increase in conversion.
You wouldn't necessarily want to track conversions for retargeting, since depending on your product or service, a second buy might be unlikely. But someone who checks out multiple product pages or articles on your site might be interested and buy in the near future. That of course are also actions bots could easily do.