I've seen enough court cases where people did not have the reasoning capability to understand the situations they were in. Not bigotry, I do believe IQ can be increased and has a lot to do with upbringing, access to info, and opportunity.

But there are people who are unfortunately dumb. Not to mock them, but understand we need to come along the simple to assist them. Because it makes for a better society.

Lots of things are used to justify bigotry. If you assume that subjectively negative attributes are a result of heritage rather than upbringing, you can use anything to justify bigotry.

For native English speakers, IQ largely correlates with general intellectual ability. People with higher IQs are generally more capable of understanding more complicated topics. It's not a moral failing to have a low IQ, and there's no reason to assume it's genetically heritable or innate and immutable.

These are not mutually exclusive statements.

For example I exfoliate with nickles because money reduces dumb dumb.

If true, then it would provide a way to redistribute wealth and measure the collective impact on IQ in a quantitative way, which would indeed make it a useful statistic

If a younger kid has a lower IQ then figuring out what skills they are lacking in to help them improve. For an adult if their low IQ score comes from lack of reading comprehension then you can assist that. The tests can help target the areas of lack.

It is not a static part of you like your height or wingspan. It can increase and decrease because of a variety of factors.