Bugs are inevitable but we should strive to have as few as possible. Your program not working right is obviously bad UX (as we've all experienced using buggy software).
The reason we have type checking is same reason we have other tooling in our editors to do static analysis like highlighting syntax errors and linting: catching bugs during development is better than finding them in production.
The reason we have type checking is same reason we have other tooling in our editors to do static analysis like highlighting syntax errors and linting: catching bugs during development is better than finding them in production.