If the firm can handle clients in 1/2 the time, they can take on more clients. They don't have to advertise themselves as being "better" or something.
Payroll, for all businesses, is a huge limiting factor on abilities. Which means, you can't just "staff up" and become larger overnight.
Not to mention, you might not require a small army of paralegals and secretaries anymore... fewer staff can get the same load accomplished.
It even opens the door to charging flat-rates for certain services, instead of by the 1/10th hour or whatever.
The point is, doing more in less time is always better... even if you decide to kick back and relax with your newfound time.
There are a few law firms that are heavily automated. But they are mostly larger, class action, pay per result, type law firms vs your standard law firm.