I don't understand use-value? Why does it matter?

Hello. Wikipedia is a great source to get a general understanding usually but it lacks in some areas. If you have questions about certain definitions and aspects of Marxian economics/philosophy I would recommend the Marxist Internet Archive's encyclopedia to get you pointed in the right direction. There is also a great video series that is often recommended here called Kapitalism101 which provides short video explanations of different concepts.

On to your question:

as far as I can tell seeks to price something based on it's usefulness to society.

Actually, use-value intends to do the opposite; it is the value in an object which cannot be calculated as a price. There is a difference between price and value in this instance, and it's easier to understand use-value as it relates to exchange-value. Use-value is the value of an objects usefulness (or utility in bourgeois economics) and it differs from exchange-value, which is the value a commodity has in relation to other commodities via exchange in a market. Whereas the exchange-value of an object is realized on the market, the use-value of an object is realized as it is consumed.

So for example if I were a capitalist who owns a factory and the labor therein to produce televisions, my prime motive is to have this factory producing televisions to be exchanged (ie to produce for exchange-value), and I have use for these televisions myself (therefore I do not get any use-value out of them). Which means I would much rather modify the production process to create televisions which would exchange for more money in relation to labour-time, even at the expense of their usefulness. The best example one could give for this concept at work is the capitalist phenomenon known as planned obsolescence.

/r/communism101 Thread