Empathy is predicated on recognizing yourself in another person's experience. This is simplest when it comes to visible or universal experiences like a broken bone. It's harder with less overt and general experiences like being suicidal. If that recognition isn't there, then empathy begins to break down.
Suicide does leave damage. The person who suicided isn't around anymore to explain apologize. Their pain has dissipated but the pain of the survivors remains and so the focus naturally falls on that. Given the taboo nature of suicide and the punitive measures taken against it, suicide has to generally be carried out in the shadows, compounding the damage it causes.
There are over 8 billion people in the world and that number is only continuing to grow. The stigma and misunderstanding occur primarily because people don't realize that we are NOT all the same. Our individual biochemistries, personal breaking points, and subjective assessments of what constitutes an acceptable quality of life are going to vary as wildly as you would expect in a complex species numbering more than 8 fucking billion. And yet these people continue to insist all of humanity with the same broad, sweeping brushstrokes. Sometimes death can be considered a more humane alternative than bringing expected to continue to endure physical and/or mental pain. Again, to grasp this really requires having been in a similar position before in life or a very robust ability to imagine, which unfortunately tends to lie beyond the reach of the average person.
Suicide may be a deliberate choice, but the circumstances that propel people to that outcome generally are anything but voluntary.