Well, the smooth leather strops aren't supposed to sharpen.
That is the thought of many of us anyways
What it does do is straighten out the edge after the steel has been bent and dented during shaving.

I have strops in about all leathers out there, some with a heavy draw, others slick as all that.
I find them all to work, and work well.
My personal preference is the slicker varieties, others prefer more draw.

If you want more draw, hand strop it vigorously and often, and it will give more draw.
Or use some neetsfoot oil, that will also give more draw.
Use only a tiny bit though, it really doesn't take much.