Aside from avoiding maintenance hassles and unhappy customers,why do we need to find bugs prior to production?
End-to-end testing provides detailed information on how individual pieces of an application work together in a specific context. When these tests fail, the bugs can be easier to find, making it much easier for developers to fix them. While this is not particularly a testing resource, having a development team that can fix bugs quickly makes it less likely that one bug could effect another.
There are many moving pieces and the faster you fix one bug, the less likely it will be to cause further defects down the road.
Because bugs that sneak into production could be detrimental to the business and the life of product.
Even on CrazyEngineers, we do thorough testing before releasing the update to the site, but still; a few bugs manage to pass our eyes. Let's say there's a bug that will fail the message posting activity - in that case this would lead all new users abandoning the site; which is not what we'd want.