Hmmm... I haven't downloaded pirated material for years now. I used to when I was younger and poorer but I don't think that's a good reason. I guess when:
1. You can't legally get the product in your region.
If enough people pirate it in your country it may make the publishers/distributors realise there is a significant market where they're losing revenue and force them to release future material at the same time as everywhere else (and this has already happened to some degree with TV shows and films in the UK).
2. If you already own it.
I don't see a problem with this if it's more convenient to download a digital copy than wearing out the physical disc. A lot of new Blu-Ray/DVD films come with a legal way to download it now anyway.
3. If the pirated copy is superior to the sold version.
This only really applies to games with restrictive DRM (although maybe to some music and films). If the DRM makes it harder for you to play your legally bought copy, whereas those who download a cracked version can play at will, then the publisher has screwed up.
A lot of this is about companies/laws catching up with the digital age. Piracy tends to be rampant when the legal means of acquiring something are long, convoluted or impossible. When companies offer a consumer-friendly, convenient and rapid way of acquiring their material, the reasons to pirate it become heavily reduced.