1. It's expensive 2. You don't know the result (he will be the work force you need for the price you want) 3. There is certain other risks like the junior goes

1. It's expensive 2. You don't know the result (he will be the work force you need for the price you want) 3. There is certain other risks like the junior goes away when he had the training because there is another company that pays more (there is allways that other company where roses are more red) 4. Why should there be training when all the people in CS are ok doing training for free at home? Hell, there is even Hackathons that are used to get creative ideas and real work done in no time for no money (nope, all the catering, fancy prices and lousy shirts didn't cost the same it would've with some senior dev's)