Because most people would rather deal with people than with machines, and thus replacing all human workers with machines would be bad for business.

Here's an example I see every week: Automated cashiers already exist - they're called self-checkout scanners. In the supermarket where I shop, the lines are always shorter (or empty) at these machines because most people prefer the checkout lanes where there are human cashiers. (I prefer the machines, but I'm definitely not a representative member of the population.)

Another example: It's nice to go to a place like Starbucks and get greeted by a friendly person who remembers you and knows what you want. Being recognized by a machine doesn't have the same feeling.

And lots of people go to financial advisers because they're unsure of what they should be doing and want reassurance. I don't think machines are very good at being reassuring yet.