Imagine you went back 100 years and someone was like "Come up with a mathematical system that can express any sequences of logical steps" do you imagine what you would deliver is a few primitives and a few simple rules and said "here you go!, this is fully complete". Its actually quite remarkable that Church/Turing didn't start off from primitives like if statements, loops, etc.

Lambda calculus is from the 1930s and predates computers, its point is that it is bare bones model of computation. It doesn't make much sense to compare it to modern languages in efficacy, as that seems to imagine someone came up with lambda calculus in 2010 along Java, C, Python, etc.

The super cool thing about it is that it is capable of expressing ALL the computation you know today, from the few primitives. An "If" statement for example is λb.λx.λy. b x y