Telltale games says the Windows Store offers wider reach than Steam, will port full catalogue there.

[JOKA_]

Bandorr said:
You google "steam" which takes you to store.steampowered.com
You click "install Steam"
Followed by "install steam now" - and you download an exe.

This isn't hard.

<snip>

So the argument of "it must be installed","must be found","is intimidating" etc all seem very, very strange to me.

 I think you vastly over-estimate the computer literacy of the general public.  These are the people that Telltale could potentially sell to on Win 10.

I don't think they're saying that Win 10 store is going to outpace Steam in terms of revenue, just that Win 10 is going to get a lot more eyes on their game that would never even attempt to install Steam.