Firstly, welcome.
Secondly though, not sure I quite get your question.
At many CPL/IR flight schools, they favour students with some experience, but not too much, so as to reduce the amount of bad habits they have to sort out.
If you are talking about flying schools, they will not turn you away unless you do not have the minimum requirements to start their course and they do not run the training required to get you there. By definition they are a flying school so students are not going to have experience!
It is not uncommon for students with Zero hours to walk in, work hard, pass everything first time and leave with fantastic results.
Very true, but also, it is not uncommon for guys to do modular training, a bit at a time and also achieve fantastic results. As you also point out some low hours guys (the best ones) go on to get jobs and have no problem passing the airline training. Getting the job straight out of training is more down to determination, a bit of luck and being good enough to pass the interview/ selection!
Surely having less hours and less bad habits has its own merits when an airline wants you to fly as They want without the possibility of reverting back to your old SOP's etc???
There is some merit in the point you make, but and this is the big but, experience counts for an awful lot, that's why airlines will
tend to want a certain experience level as you can't beat real life exposure when it comes to flying aeroplanes. Most experienced guys have more capacity and easily adapt from one airline to another and although your point about previous SOPs is an issue, it is by no means insurmountable. I have been through 4 different sets in 12 months and yes it is a problem, but with time it doesn't take long before you can't remember the old ones! Bad habits are something separate and that comes down to individual professionalism and a good training department!
Hope that answers any questions you raised.
PP