This really wouldn't bother you??? You really wouldn't mind not knowing?
One giant reason that knowing for sure would be helpful is knowing that you're less likely to get reinfected, and likely less likely to have serious effects if you do end up reinfected, if you previously had it (even if blood antibodies have faded, your T memory cells may still help you out). This might change your behavior going forward.
However, on the last point, I'm afraid that thinking might potentially prove quite dangerous. As far as I can tell (from closely following the medical literature, though I am not an immunologist and don't claim any authority on the subject) we really have no idea as to how quickly immunity decays, every single cellular immunity (T cell) study I've seen is extremely limited methodologically and we have no clinical evidence whatsoever to suggest that reinfections would have a milder course. If that turns out to not be the case, people who behave incautiously based on their test results might significantly endanger themselves.