ACH in the US is not simple to use. Companies that accept ACH payments are using a payment processor that comes with a fee (usually less than credit card fees); contractors aren't going to set that up. Consumer to consumer transfers built on ACH have increased in the last couple of years, but with low limits, inappropriate for contractors, and generally with terms of service prohibitting business use. It's easy to move money between my accounts with tools based on ACH, though. There's nowhere at my bank where I can say send $x to a routing number and account number, it takes a bunch of setup work.

Wire transfers are expensive here; my credit union which doesn't generally have high fees, charges $29 to send a wire (they don't charge for incomming wires, but some banks do). I've had some brokerages with free wires, but usually that's tied to a balance requirement or in connection with a company sponsored account (for stock based compensation or retirement accounts).