Because it forces classifying workers as either employee or contractor when a case could be made for another classification of flex-employee.  So, for example a good number of über drivers are part timers, which is fine, but if this becomes a normal aspect of the economy, we need to be able to make it automatic for this class of people to get some kind of benefits.  Not as much as employees, and more than [$0] as in contractors who need to do their own taxes, benefits, healthcare, etc.