Not sure where you are, but here in the US wire transfers are slow and also expensive. Last time I had to do one internationally, it took several hours to clear and cost me something like $30.
NACHA (the U.S. body that governs ACH transactions) just started supporting international ACH transactions over the summer I believe. An ACH transaction typically costs the consumer between $0-5 (depending on how quickly they want it sent) compared to a wire transfer that could be $50 or more.
Yes, because of the regulations. If you have any history of transfers then you're usually approved within minutes vs occasional usage. You can also improve the speed by using an abstraction service like Paypal which offloads some work while charging more for the risk.