You are mistaken, I work for one of these. I have 12 years experience and I have only one failure to deliver and it was stopped in the design phase because it was too complex and the client wasn't ready.
I worked for one too and I can't say the same thing. Entire projects were poorly thought out, designed and improperly executed. The people working for the company were incompetent and their "hiring bar" was if you had a pulse. And this was a big well known firm.
Same experience with me. I have mostly only consulted with large companies. There are some companies that insist on solid code and design. There are others that just live from quarter to quarter and the whims of the CEO and just throw out whatever is done at the end of the quarter. Having a great lawyer team chomping at the bit for litigation helps their confidence in living from quarter to quarter.