I am/was in the same boat as you: For a long time, I just didn't care that I was giving away a bunch of information in return for convenience, and didn't get why people cared so much.

I don't really know what triggered it, but at some point I became painfully aware that the only goal these companies have is to squeeze every possible penny out of selling me. I started noticing that the stuff they ask you to confirm is 95% stuff they want because they can sell it, or use it to get you hooked to their service, and 5% (at best) stuff they need to make the service good for you.

This triggered a change in my perspective: Now it pretty much makes me sick to my stomach to think about all the companies that are drooling over me, trying to make a buck by getting me to click something I'm not actually interested in, or don't actually need.

These people have a vested interest in manipulating me, and by giving them my data, I'm giving them the tools to do it. I don't want to be manipulated or sold as a product: That's what made me start caring about protecting my data.