There is no strictly mathematical answer to this question. It has to do with the long history of mathematics. For thousands of years, negative numbers were not used in mathematics and hence did not exist. All numbers were positive and the positive versus negative number concept did not arise until a few centuries ago. For example, from Wiktionary article positive
Of number, greater than zero. [from the 18th c.]
More information from Latin Stack Exchange question 1438 "Negativus and Positivus".
The use of “positive” and “negative” as opposites is surprisingly modern. It seems to have originated (or at least been popularised) in the context of modern (i.e., 17th-century) mathematics with the distinction of positive and negative numbers. “Positive” numbers are numbers that you can posit, put on the table, observe as objective reality. “Negative” numbers negate the corresponding positive numbers (positive 1 plus negative 1 makes zero). A century later we get also "positive" and "negative" electricity.
So, it seems safe to state that "positive" numbers are more fundamental than "negative" numbers. If the word "real" had not already been used in the context of numbers, we might have called numbers greater than zero "real" numbers or "actual" numbers, and to borrow a phrase from John Napier, we might have called numbers less than zero "artificial" numbers. Of course, all this is just giving ideas conventional names. The "imaginary" numbers are slightly more imaginary than negative numbers. The "complex" numbers are slightly more complicated than real numbers, but all this is just a naming game and changes over time.
To state the obvious, when we refer to or write the number seven we write just $7$. To refer to the additive inverse we need to use "negative" seven and we need to write $-7$ which is strong evidence that the positive numbers are more fundamental than the so called "negative" numbers since we can only refer to them in terms of positive numbers.