Say you're a parent. You ring a tuition agency to try to find a tutor. You're told there is a good tutor in your area but she is only available during the daytime - does your child go to a college or sixth form where they only have to attend when they have lessons? You lie and say yes. Then when you speak to the tutor, you waste vast quantities of her time getting to the point that in fact your wonderful child can't possibly come during the day - any day, only at weekends.
I can understand if there was any hesitation in my voice, or if I used indirect phrasing to try to let you down gently. But I've got used to over-pushy parents and am now utterly blunt up-front. If I state categorically, "No, I cannot take on any more students at weekends. I already work all day on Saturday and all of Sunday morning and I do not want any more weekend work." - why in God's name do you insist on repeating the facts that your daughter can't possibly do a weekday evening because she has so much homework? Do you think I'm honestly going to stop and rearrange my entire schedule, and ring a load of existing customers to try to move them around for you, a brand-new customer who may well only come for 2 or 3 lessons and then give up?
How difficult is it to understand that if I am a good tutor, I have already been booked up well in advance? It's the middle of November and the exams are in January. Most of my existing students arranged lessons in early September, or even over the summer. The only new students I've taken on since September have been people who were free at least one daytime. There's a limit for the number of hours I want to work in a week. How many people want to work every single afternoon and evening and from 10am-7pm both weekend days? When am I actually supposed to see my friends or family?
"No, I'm sorry, I really don't have time. I'll ask the agency to send you another tutor" means No, I'm sorry, I honestly don't have the time to teach your kid. Not "Why don't you get your kid to ring me and waste yet more of my time?".