The quality thing... In Aus, they don't get many men offering to donate because they have to agree to be contactable after any resulting child turns 18, and they don't get paid for it... so here they pretty much accept everyone that offers, as long as they don't have any diseases.

In the US, they pay them well for their donations, and men can still choose to be unidentifiable. As a result they get many more men offering to donate. According to the website of the bank I'm using "Less than 1% of the men that ask about being a donor candidate are evaluated. Less than 5% of the candidates become donors" - so you can see they can afford to be very picky and only keep the donors with the highest sperm quality - measured as motility and count after freezing.