[tombert]

Assembly is higher level logic than brainfuck, especially on modern chips. You have built in instructions for arithmetic and conditionals/branches and you can allocate memory and point to it.

You don’t really get any of that with brainfuck. You have a theoretical tape and counters and that’s basically it.

[eru]

SKI calculus is pretty neat, too. You get no tape, no counters. (But it's not quite as bad to program in as brainfuck, because you can built more ergonomic contraptions to help you along.)

[arethuza]

SKI can, of course, be de-optimised a bit further by replacing I with SKK. You are right though that it is relatively simply to go from something that looks like a normal program languages to a pile of S and K combinators. Not the most efficient way to compute though!

[somat]

Unlambda solves that problem.

"What if we had the lambda calculus without the lambda forms?" asked no one.

http://www.madore.org/~david/programs/unlambda/