make 'when' parameter of start() and stop() optional?

Is there a reason not to make the first parameter of
AudioBufferSourceNode.start()/stop() optional? Seems like it would be
convenient to have it just default to zero so authors could write
"node.start()" to make it play "right now", and ditto for node.stop().

Rob
-- 
Jesus called them together and said, “You know that the rulers of the
Gentiles lord it over them, and their high officials exercise authority
over them. Not so with you. Instead, whoever wants to become great among
you must be your servant, and whoever wants to be first must be your
slave — just
as the Son of Man did not come to be served, but to serve, and to give his
life as a ransom for many.” [Matthew 20:25-28]