It's ease of use. Elm first and foremost teaches programming. That happens to be in an exclusively FRP style, yet it ignores the usual evangelism. It is a practical language with automatic type inference and a simplified syntax.

But elm is a step on the road to a future where I believe that, when the dust settles, it will acknowledge that iteration, map, filter and reduce are as elementary as if-then-else.

So these operations (and if-then-else) will gain an iconic representation in the syntax, like punctuation. There is no need for words to be reminded of their function, the mere appearance of the program should suggest the flow and transformations they implement instead.

In other words, current languages are not FRP languages yet, but elm comes closest.