And how long does an average civilization broadcast radio?
On the "life is safe" end of the spectrum, maybe there's much better technology to be discovered. On the "life is dangerous" end, maybe you learn pretty fast not to broadcast your location to the galaxy.
Obviously we don't have much to draw on, but it seems like our technological growth looks a bit exponential. I'd imagine a civilization that has been around for a million years would have discovered a hell of a lot of technology - but a million years is a blip in 13.82 billion years, the age of the Universe. It's like 0.001% if I've got my maths right.