[R] curious about dimension of 'apply' output when MARGIN=1

[Benjamin Tyner]

Reading the documentation for 'apply', I understand the following is 
working exactly as documented:

 > M<-matrix(1:6,ncol=2)
 > M
     [,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6
 > apply(M,2,function(column) column+c(1,2,3))
     [,1] [,2]
[1,]    2    5
[2,]    4    7
[3,]    6    9
 > apply(M,1,function(row) row+c(1,2))
     [,1] [,2] [,3]
[1,]    2    3    4
[2,]    6    7    8

I'm not proposing any changes or extra arguments to 'apply'. Rather, I'm 
wondering what is the benefit for (or rationale behind) this somewhat 
unintuitive behavior in the case that MARGIN=1.

Thanks,
Ben