Well, because it doesn't. At least on the Linux version I used in the past, it defaulted to 512 byte blocks or something similarly small and it commits every block individually, leading to really slow performance with USB sticks with controllers not smart enough to bundle writes together. I wouldn't be surprised if that incurs some heavy write amplification at flash level too. Perhaps it's smart enough to figure a better block size now but this is where that habit comes from.
Another thing, creating sparse files with the seek option (simply put files containing zeros that are not actually written to the disk nor taking space, but do turn up all these zeroes when you read the file). Also something not duplicated with cat or head.
What I like about dd is that it can do pretty much all disk operations in one simple tool. Definitely worth learning all of it IMO.