Those contact forms usually require a phone number. And very often the contact, when if it actually comes, is by phone. If I want to contact a business by phone, I'm perfectly capable of doing so, probably at a time which I deem to be at least moderately convenient. If I'm contacting them textually, that's what I'd prefer by way of a reply...
I assume this becomes even more annoying if you're avoiding the phone due to disability rather than just preference.