Why does Realty Brokers don't train Realtors that they recruit to join their office after they recruited them?

Many of my realtor friends said about this issue. LIcensed brokers are so stingy on even showing their recruited realtors (new ones) what the step by step way to sell and buy the house. Even though for the fact that these newly recruited realtor have no idea what the first thing to do. They just show the bathroom, and where to get the coffee and that's it - you're on your own - even though they promise to train them - they will just bill the new realtor on something the poor realtors didn't even understand what the heck they were billing for? Is this really legal in this business? Isn't that if they train the realtor completely, they will tend to work hard and be loyal to the employing broker? The more the realtor work hard - the more commission split the broker will get - isn't this the fact? Plus, if the realtor is happy with his/her broker, the broker will get a lot of referral from the realtor when the realtor decided it's time to quit.