Why does BattleNet randomly uninstall games?

So, I bought WC3 Reforged a couple weeks back. 30gb download. Played through several campaign missions before setting it aside for a week. Then I went to play it today…and it had been uninstalled. By Battlenet, without my input. Now I have to wait while it re-downloads and re-installs. And despite my high-speed internet, the download speed is averaging ~700kb/sec…for a 30gb re-install. Unacceptable.

This isn’t even the first time. At least once a week my son complains about BattleNet uninstalling Burning Crusade Classic and all his addons on his computer.

So, WTF Blizzard? Fix this!