Why did they separate Cas and non-cas?

[DeucesAx]

Is that it? It boils down to me either wanting 3.46... or 2*sqrt(3)? Why not just something more like press enter for exact and shift enter for approx? (I don't even have the calculator yet it arrives Monday, but I really need to hit the ground running with it)
Can I turn off the default setting that each variable is initialized as 0 in the home mode? Im scared I forget about that in an exam.