If I read your email and then selected "metadata" I found important, walked into a very busy public square, and started shouting your secrets you'd be right to be uncomfortable. If I, for example, made a reasonably accurate prediction that you are pregnant/on drugs/have ED/etc and then told 10,000 people about this you'd be right to be angry.
Yet...you're okay with a company doing any of this? Is it because you can't see it or feel it directly? The head in the sand approach doesn't work. With enough datapoints in one bin anyone can use "metadata" to make extremely accurate predictions about your private life. You need to defend yourself from the constant gathering of this metadata. Snowden warned us and apparently very few of us decided to listen. All it takes is one leak, one hack, one disgruntled employee, or one bad government to take all those secrets you're not thinking about and turn them into weapons to use against you. In a modern battlefield you are a target and the war has been going on for decades now.