Debit and credit transactions can be reversed for months, with the merchant losing almost every time. After 3 confirms your golden, so waiting 30 minutes is not a bad deal. (Even after 1 confirm it is still a million times more secure than any credit or debit transaction imo)
Not sure where this went with regards to mining or mining hardware, but w/e
I'm not even sure why it's three confirmations- I've virtually never seen a double spend with more than one, and it's also very difficult to pull off. The point is that it's incredibly secure, the main reason why I use Bitcoin for most of my digital transactions.