Well. If you are going to be transacting with a retailer, you would not want your information to be leaked. This is one purpose of bitcoin. No need to share unnecessary information to strangers that could later on use this against you in some way.
if you buy things at any retailer in person they have video cameras all over the place. no matter how you pay you're on video and they know exactly who you are. so the payment method is pretty much irrelevant you're not anonymous. plus the video could show you actually using bitcoin as payment. now the whole world knows or potentially could know that you use bitcoin. the people that run the cash registers will know. the security who watch the video cameras might know. you're not as anonymous as you think.