Why are Joomla url query strings commonly delimited with “&” instead of “&”?

I often see Joomla url querystrings with & delimiters between key-value pairs instead of the standard &. In a previous question, How to make my Editor plugin (type: editors-xtd) survive after updates?, I demonstrated the call of http_build_query() (which I think more Joomla developers should adopt as standard practice to improve code readability and stability)…