Well, you can't switch arguments mid-way.
All those people that you claimed replaced their smartphones with tablets when they go to conferences, used to bring laptops before smartphones. Weren't you paying attention?
So it went from paper pads, to tablets, to smartphones, to tablets.
That means that at least some businesses did dump laptops in favor of smartphones for at least some functions.
I know you are trying to be all smarty-pants with your straw-man argument pointing out how tablets are not going to replace laptops completely, in every facet of business--but nobody is claiming that.
What some of us are saying is that, there are some functions for which laptops and desktop computers used to be regarded as the most appropriate tool, and now tablets are taking their place.
Not only that, but tablets are being put to some uses by businesses to which laptops or smartphones weren't even considered.