Yes, if you take precautions you can be safe for some purchases, but if buy, say, a house or a car, which necessarily has your name on it, then people can trace backwards to find you, and then extrapolate other purchases etc.
For GMail, on the hand, you don't have to be careful, you just use it and nobody without a court order is going to be reading your email.
And yeah, I guess if we're talking about one's spouse, that's probably correct, but if we're talking about malign actors e.g. people looking to steal something from you, spending without taking precautions with Bitcoin can get you ripped off, whereas you can email your brains out with GMail and never have to fear such a thing.
For the average user not accustomed to tradecraft, a centralized app from a reputable company is a better bet than Bitcoin or most other cryptos (obviously not the ones specially designed for anonymity like Monero).
And for most people who are not criminals, the kind of anonymity you get from centralized apps is perfectly fine.
Of course if we're talking about credit card purchases (or PayPal et. al.) then it's is a totally different story. Your purchases are practically announced to the whole world with that because they sell non-anonymized marketing data to whomever wants to buy it.
What somebody needs to do is marry these two concepts wherein you can make payments anonymously with a centralized digital currency architecture that doesn't sell your data (and doesn't even know who you are), allowing average consumers to make anonymous payments and yet not be a security threat by allowing criminals a means of extra-legal payment.