# How does steric hindrance cause sulfur hexafluoride to have almost no reaction chemistry?

Sulfur hexafluoride ($\ce{SF6}$) is, according to the Wikipedia page, a hypervalent substance. However, according to the page in regards to $\ce{SF6}$ reactions:

There is virtually no reaction chemistry for $\ce{SF6}$. The main contribution to the inertness of $\ce{SF6}$ is the steric hindrance of the sulfur atom, whereas its heavier group 16 counterparts, such as $\ce{SeF6}$ are more reactive than $\ce{SF6}$ as a result of less steric hindrance

The linked steric hindrance provides many examples of how that chemical process works, but specifically, what steric hindrance (or any other) mechanism results in $\ce{SF6}$ possessing virtually no reaction chemistry?