This isn't necessarily true. You can mix white with the colours to get a pastel shade first go. I've done easy mesh pastel pink on platinum blonde so that it was blonde with fine pastel pink highlights.Only downside is that you have to dye it a brighter colour at first to get that nice pastel look after a few washes. If you just go dye it a pastel colour you run the risk of washing everything out and just being blonde.
But I agree, pastel colours are less dangerish and more people should try them.