So I was trying to get the ScriptingOptions happening, and this is the only way I've found so far. It's ugly, and if you have a better way of doing this, please post a comment for me.
$so = New-Object Microsoft.SqlServer.Management.Smo.ScriptingOptions
$so.DriAllConstraints = $true
And this gives me the Sales.Store table with all the default constraints thrown in. Much better. Ugly way of doing it, but at least it works.