Some customers - not saying this is you OP but if it is then it's an explanation - just come across as total nightmare customers.
Some are "talkers" they follow the tradesperson around chatting in their earhole about endless crap, while they are trying to measure up, and the tradie can barely get a word in about the actual job. The tradie just dreads working with them as they don't think they'll be left alone to get on with it.
Some are just umm and aaahers. You can tell they don't know what the hell they want, or whether they have the money, or if they're going to move or not, or if they want to spend £2k on a holiday instead. The tradie worries he'll get messed around with either them getting back to him, or getting paid at the end.
Some advertise the job on facebook and say something like "cheap as possible please" no decent tradie ever answers these, you'll only get crappy desperate people. They'll worry you'll want to cut corners or won't pay at all when the job's finished.
Sometimes the house is an absolute shithole and smells and the tradie doesn't want to work there or they come across really snobby and tradie just doesn't think they will gel, or they've got a really annoying yappy dog, or they bang on about how they're an "engineer" and you just know they'll be a pain in the ass and question everything, leaving the tradie wondering why he got him in if he can do a better job.
And sometimes it's not you at all, the job itself is just annoying and there's an easier one waiting round the corner which pays just as well
If he says of of this to you, he risks offending you and damaging his reputation. It's a real risk and worry that a disgruntled person you measured up for once and didn't want to work for is going to go on google and leave you a really shitty essay of a review and in just five minutes of meeting someone, your business is ruined.
So he fobs you off with an excuse about being busy between now and Christmas (actually that's probably even true - everyone likes to get their house done before Christmas so it looks nice for hosting and they're not left dealing with half done jobs over the period) and hopes you'll get the message. You don't and keep asking - so he blocks you and hopes you think something happened to his phone or something.
Right now, it's a tradesman's market. There's plenty of work and the tradesperson can pick the jobs they want - within reason - so it's worth actually trying to make your job attractive to the tradesperson, not just assuming everyone must want your job .
I honestly hope that helps. I'm just trying to give an honest perspective.