Why will this function run only once on click but after that it stops working

Question

Why will this function work only once? I'm expecting it to keep adding values to the page, but it only does the conversion one time and after that it stops reacting to button clicks:

let myButton = document.querySelector('#convert');
myButton.addEventListener('click', function() {
  let finalResult = converter(document.querySelector('#myInput').value);
  document.body.innerHTML += finalResult;
})

function converter(value) {
  let conversionResult = (value - 32) / 1.8;
  return conversionResult;
}

<input type="number" id="myInput">
<button id="convert">Convert</button>