Really? Can you list the lisps (common lisps, schemes, whatever) that let you do this kind of stuff? And tell me why the ones that don't aren't "serious", according to you?
So, according to you, Python isn't "general-purpose" and Haskell isn't "serious"? I could list many more languages here, of course, but my point is obvious.
It's useful to be able to do lowlevel bitflipping stuff, that I don't deny; and I am suitably impressed by the number of lisps that have put thought into allowing this. But just because a language lacks such capabilities doesn't mean I'd rather use C, or even Lisp! And often, if I'm really interested in lowlevel stuff, I'm also intimately concerned with things like speed and memory usage that I can't necessarily address even in a highly optimized lisp. For example, all lisps need GCs (what if I want to write a GC? I'd rather not have my GC itself need GC, and I'm not learned enough concerning the implementation of eg. SBCL to, like the writers of T, write a GC in it such that the GC needs no GCing), and any Common Lisp necessarily comes with a huge standard library attached.
