R help - Oct 2003 - loglm() uses only a reference to data, and not data itself - is that on purpose??

Dear all,
Consider the following:
 
library(MASS); data(HairEyeColor)
l1 <- loglm(~ 1+2+3, data=HairEyeColor)
myloglm <- function(){
  nd <- HairEyeColor
  v <- loglm(~ 1+2+3, data=nd)
  return(v)
}  
  
l2 <- myloglm()  
  
Now, step(l1) works, whereas step(l2) does not, the problem being that data nd
does not exist outside myloglm. I was under the impression that objects from
functions like glm() and lm() "carried their data" with them, but that
does not seem to be the case for loglm(). Is there a reason for these different
behaviours??
 
Thanks in advance
S?ren H?jsgaard