Simply because that's not how native English speakers word out.
There are languages that word it that way, so it can make sense, but it doesn't in English because we word it differently. Some other languages word it similarly to English as well. Our way also makes sense (but not in languages that think about it in a different way).
For right, wrong, or indifferent, English speakers do not have years. Instead, they are a certain number of years old.
I saw the comment where you said you forgot the YOU in the question (which is required in English, but again, in some languages, it isn't).
Different languages do things differently.
Although I imagine there are languages that allow both ways of thinking about, the few I know well enough use one method to talk about age: years old (or something very similar) or having years. One or other, not both.