gankplank in competitive

I've been watching a bit of competitive matches, and I'm always surprised to see gankplank picked in the top lane a lot. Probably I'm missing something, but I don't see him being useful: he does not have great ccs, his big source of damage (barrels) is very counterable, he does not have gap closers (except his speed). Is it because of splitpush potential or the global ult? what am I missing?