Yeah. I know, but (at least in modern times) Mac has been associated with Scots, while Mc has been associated with Irish.
I've got both in my family. It gets confusing .. ;-)
I think it had to do with prejudice against the Irish in the mid to late 19th Century, but only in the US. Some people changed their spelling to differentiate Scots from Irish; but it wasn’t general, so it’s not possible to tell who in America is Irish or Scottish by the spelling; you have to know the origin of the name. My Scots always spelled it as Mc, with a little mark to indicate abbreviation; they never changed it.
-JT