The answer to this should vary by the functionality of the software. If I have a program that calculates projected weight loss and it's only used by me on my computer, crashing or displaying obviously incorrect values from accepting negative values for weight or body fat percentage only impacts me so it's mostly a user friendliness issue. If I'm entering my billable time into my employers time tracking system, anything that could corrupt data impacts more than just me. While I could intentionally lie about my billable hours without detection, I shouldn't be able to accidentally or intentionally enter that I worked -5 hours or 5000 hours on a particular day. Accepting either is undesirable and impacts others.

I'm confused why the parent comment is being downvoted. It's a valid question. It might sound naïve to some but it's still worth discussing.