The superdraco engines in Dragon have a printed combustion chamber. But these are (relatively) low pressure engines.
Chamber pressure is limited by the fuel injection pressure. The simplest, fastest response time way to provide the fuel pressure is to use a high pressure bottle of gas to push the fuel through. Since those are important features in a launch escape system, that's how superdracos work.
But... chamber pressure is directly correlated with efficiency, so a main engine uses an extremely powerful fuel pump to achieve higher pressures.
That fuel pump is itself, a rocket engine with a gas pressure fuel system like the superdracos.
Chamber pressure is limited by the fuel injection pressure. The simplest, fastest response time way to provide the fuel pressure is to use a high pressure bottle of gas to push the fuel through. Since those are important features in a launch escape system, that's how superdracos work.
But... chamber pressure is directly correlated with efficiency, so a main engine uses an extremely powerful fuel pump to achieve higher pressures.
That fuel pump is itself, a rocket engine with a gas pressure fuel system like the superdracos.