That's mostly because they are sensitive to brand damage in ways that Uber and Tesla (not Google) are not.

Mercedes or Volvo getting caught with a product in the ways Tesla has been getting caught would be unacceptable to their customers. The brand damage would be massive. Tesla as 'the new kid on the block' has a lot of leeway to mess up that you would never accept from an established brand. The whole autopilot saga is an excellent example.

By the time Volvo or Mercedes release a next level self driving car you can simply expect it to work, all the time. Until then they will release small incremental steps on their 'driver assist' technology.