Why is iPhone data storage so bad?

People are constantly having memory problems with iPhones. On my iPhone 4S running 6.1.3 I have 2.3 GB available. I want to download Asphalt 7, which is only 1.41 GB, but it keeps saying that there isn't enough space. Last time I checked 1.41 < 2.3, so what's the problem?

I don't understand why people post iPod or iPhone memory questions and don't specify how their device's memory is being used.yes, that matters.