Because most people are working at Failure/Feature factories where they might work on something and at last minute, they find out something is now warning. If they work on fixing it, the PM will screaming about time slippage and be like "I want you to work on X, not Y which can wait".
You found that out at the last minute. So then you did a release. It's no longer the last minute. Now what's your excuse for the next release?
If your management won't resource your project to the point where you can assure that the software is correct, you might want to see if you can find the free time to look for another job. You'll have to do that anyway when they either tank the company, or lay you off next time they feel they need to cut more costs.
2 Years later, you have hundreds of warning.