Stepan is like the Swiss-army knife of players. He's a center who can penalty kill, play on the power play, play a defensive shut-down role, and puts up some offense, and can take face-offs. Granted some of these roles he might be more of the toothpick or tweezer level of contraptions on the knife, but the point is that if Tocchet needs some one for just about anything, he can fit Stepan into that line and it'll be more cohesive than many other options. It's what's allowing him to play up and down the entire lineup whereas some guys need to be top 6, or others who are absolute black-holes on offense, he at least can fill in until you find a more dedicated tool.
The plan has always been for him to mentor the young guys as they attempt to hone their skills on the top lines while he corkscrews his way down the line-up, yet remains a fixture. It makes sense that some one who fill in so many roles would get more ice-time, and it's probably less about him getting the ice-time versus some one else taking that time away from him. I assume he'll be a more permanent fixture in the bottom 6 once Dvorak, Schmaltz, and Hayton have fully ensconced themselves in the top 6 as viable centers.