While, I don't think what those coaches are doing is a total waste, I have found from personal experience it certainly is ineffective and . Our program previously had a very "people will come to our school because it's the right school for them" and just waited to see who was interested in us, and these letters are a pretty similar approach. The letter takes a slight step farther by actually providing kids with information about the school, but unless they're really interested in some specific program at the school most people don't sit down and just read pamphlets.
Our program has EXPLODED in the last 3 years. For men's and women's XC and track combined we have had over 30 incoming student athletes the last 3 years (freshmen and some transfers. 4 years ago we had 43 total athletes). This isn't an accident. We don't just shoot out information and hope that someone will bite, but we also don't sit down and research and personally contact the thousands of kids who could impact our team from the state of Virginia. We want people to know who we are and what we're doing so we go out and actually meet people. Our recruiting is super coach based. Coaches know the personalities and strengths of their athletes, so we talk to them about what we have and who will fit with us. We go to as many high school meets as we can make it to, and we talk to the coaches at just about every good program, about who we are, the progress we've made, and which of their kids we've noticed. It's all building relationships on multiple levels.
It's one thing for me to send you a form letter and say this is what we are and what we're looking for, but it's a completely different thing to come see you at a meaningful competition, explain why I'm interested in your program, and tell you what my program can do for you athletes. People don't get to know form letters, but they have gotten to know our program and that has caused them to champion our recruiting. Coaches and athletes from schools we haven't talked to before know who we are and are looking at us by reputation of those we have recruited from.
If you're a D3 coach and you're not getting out to see kids race, and meet as many HS coaches from your target areas as possible, you're getting left in the dust.