Why do logicals (booleans) in R require 4 bytes?

Question

For a vector of logical values, why does R allocate 4 bytes, when a bit vector would consume 1 bit per entry? (See this question for examples.)

Now, I realize that

Answer 1

Knowing a little something about R and S-Plus, I'd say that R most likely did it to be compatible with S-Plus, and S-Plus most likely did it because it was the easiest thing to do...

Basically, a logical vector is identical to an integer vector, so sum and other algorithms for integers work pretty much unchanged on logical vectors.

In 64-bit S-Plus, the integers are 64-bit and thus also the logical vectors! That's 8 bytes per logical value...

@Iterator is of course correct that a logical vector should be represented in a more compact form. Since there is already a raw vector type which is 1-byte, it would seem like a very simple change to use that one for logicals too. And 2 bits per value would of course be even better - I'd probably keep them as two separate bit vectors (TRUE/FALSE and NA/Valid), and the NA bit vector could be NULL if there are no NAs...

Anyway, that's mostly a dream since there are so many RAPI packages (packages that use the R C/FORTRAN APIs) out there that would break...