Why is testing of final product is important in any industry?

Being Quality Assurance and Testing Manager for the last2 years working for Free and Open Source Software Communities, I can assure you that it is very important to test any kind of product before you let your clients/users to use that. Whether it is a software or a hardware or whatever product it is, testing is a must. That is of course, if you seek a good quality product but if you care less about quality, then you might not focus on testing.

The more you test that product, the more bugs/errors/issues/problems you may find and that is better. Again, if you are interested to improve your product then you need to keep testing.

What myself and my team do, for example, is: we do release a new version of a Linux Operating System (Ubuntu, Lubuntu, Ubuntu GNOME and other systems) every6 months. Once we release a version, we take a week or two as a rest then start all over again to work and prepare for the next release. We will have less than6 months to work on a version and test it before we release the stable version. The more and longer we test, the better.

Hope that helps!

P.S.

Testing in general applies for everything, not only software :)