Last year's macOS Sierra won't install on my wife's 2010 Macbook Pro. Apple doesn't seem to always roll off support every year. I'm guessing some version adds

Last year's macOS Sierra won't install on my wife's 2010 Macbook Pro. Apple doesn't seem to always roll off support every year. I'm guessing some version adds new tech and they drop support for 3-4 years worth of hardware all at once (that hardware is usually at minimum 5 years old).