I put my hose behind the steps when I refill and that washes some of the dirt out. I also push water against them when I brush to help circulate there. And, when adding bleach, I pour some of it directly behind the steps.
A couple of times during the swim season I move the steps and brush under the bottom step.
I don't stress out over dirt or algae under the steps as long as it stays there. If it starts to creep out I spend a little extra time brushing around the bottom step.