I used to tell myself the same thing. Then one day, a customer misconfigured their NetScaler, and all hell broke loose. We had half-delivered CSS files, misfiring form handlers, random blank screens of death, and a buggy front-end library that would bombard the backend with requests if it received the wrong status code with no back-off logic! There were hundreds of bug reports. You name it, we had it.
Debugging everything was just wild, especially with the constant tension of "What if it's our fault?" In the end, it wasn't! We got paid for our time, and we were able to close a massive number of tickets. It was one of the best weeks of my professional life.