This is something I just don't get. Ever since I heard about the launcher I have loved having it. The ability to have all of Blizzard's games under one launcher/manager has been awesome. Knowing that the launcher has tied itself to my computer so I do not need to authenticate on a regular basis, including pulling up my account management page from the launcher. Not having to wait on patch days for the patch files to download (in recent memory hearing my friends/guildmates groan as they had to wait while the D3 pre-expansion patch had to download and knowing that mine already downloaded without me even playing it recently so I could jump straight in). Being able to see which of my friends are online in each given game before I log in is also pretty nice. The only thing the launcher does is quality of life improvements, so I do not see why so many people have so much against it. It's as if these people don't like Blizzard trying to make it easier and more convenient to get into their games.
I know some people like to complain just to complain, but it seems pretty extreme in this case.