In my college life I have had many different types of professors with lots of different types of personalities. There seem to be some that give you all the answers and some that give you almost nothing to work off of. Laziness or over diligence it all depends on how you look at it because it can sometimes be helpful either way.
Giving too many answers limits the ability of students to solve their own problems. Those students that want to learn will naturally seek out answers and try and raise their grades. Those that don't want to learn won't take the extra step to find something new out.
Here is the problem. In any particular class you are likely to have lots of different types of students. Some that want to learn and will do it in any environment and those that don't want to learn. For the latter, you will need to drag them through the educational process but this isn't necessarily the professor's issue.
Putting comments in the papers and pointing out areas of improvement, where additional help is needed, and where to find information is important. Creating awareness of the issue is important but the student may need to follow up on their own to obtain additional information. That is their job as a student.
The professor's job is not to provide all the answers or make the learning process super easy. The student should struggle a little as they master new ideas. Researching solutions is part of their job. However, it is necessary to impart wisdom and advice and tell the student where they can find additional depth and information as needed.