Why is ignoring autocommands necessary?

[lifecrisis]

Why does every NERDTree command ignore autocmd events? I had a nice idea to enhance my NERDTree, but this gets in the way. I suppose there is a good reason for it, but I'm still curious.

" FUNCTION: nerdtree#exec(cmd) {{{2
" same as :exec cmd  but eventignore=all is set for the duration
function! nerdtree#exec(cmd)
    let old_ei = &ei
    set ei=all
    exec a:cmd
    let &ei = old_ei
endfunction