Most companies aren't software houses.

If you fulfill your delivery contract in half the time, great for me, you now need track down another customer.

Or put in another way, an agency now only needs a third of previous team sizes to deliver the same amount of work.

The other two thirds might be lucky to have another project assigned, or get to seat on the bench, and depending on the world region (offshoring shops) get their salary halved, before being fired if seating too long on the bench.