Why nobody is using Tahm Kench as a top laner?

Now that Tahm Kench is released, I am seeing many people testing him, but pretty much nobody is using him as a top laner, even though he was made to be one. Why? Why he is more popular as a support? I thougth that Riot was going to introduce champions based on their position: they would introduce a jungler, then a sup, then a mid, then a top, then an ADC, then another jungler, then another sup, and so on. But apparently Riot broke this chain, because they introduced 2 supports - not in a row, but there was only one champion between them.

I guess that Tahm Kench is suffering from the effect where he is extremely popular on a lane but is still viable on another, you just don't see anyone using him on that other lane.