They are skewed to mathematical ability because they are designed by psychologists, psychologists are favoured to academic achievement, and academic achievement is favoured to mathematical ability. Educated people, in the sciences, tend to equate mathematics with logic, but that is only sometimes the case. There are many kinds of IQ tests. The standard ones tend to correlate very highly with algebraic proficiency. There are logic IQ tests by which those who are not gifted at algebraic thinking can score much higher than those who are. This accounts for the high Asian IQ, for example, in my opinion. Asians with score better on common IQ tests, even though, as we all know, they are retarded.