keylighting not going to feet

I am a programmer/designer for live music, mostly doing shed/arena shows. This includes keylighting. When using a followspot (normally, these days, robo spots, but also applies to traditional RJ-style followspots) I’m always making the focus head to toe.

Now, I also have season tickets to a large theater in my city, and every single time I go, I’m confused why the followspots have focused so narrowly that you can see almost only the performer’s head, maybe a little bleed lighting their torso, and their feet are more or less in darkness.

In fact, I went to see the Tina Turner musical this week, and the entire time it was the same situation, EXCEPT for when they were emulating one of her concerts, and they widened the focus and got her feet in as well. Song finished and they went straight back to torso/head only.

Is there a reason for this? It seems so surprising since costume design is such a part of live theater, and I’m constantly wondering what they’ve got on their feet.

What don’t I know?