The quickest answer is because we aren’t beholden to official titles.
On the latest episode of Nos Audietis, during the introduction of head coach Brian Schmetzer you may have noticed the following exchange;
Jeremiah Oshan: Brian, obviously you’re the head coach of the Sounders right now -
JO: I’m calling you the head coach. We’re not using interim.
That may seem odd. The Seattle Sounders are quite clear that Brian Schmetzer is the Interim Head Coach. One need only look at the video boards during the prematch announcements, or any press release, to see “interim” all over the place.