Why don't recruiters care about contractors

Is it a good idea to use recruiters to find jobs in the software industry?

Yes No. Getting a job is your first priority, and the channel doesn't matter.

The ideal position of a recruiter is to profitably place a suitable candidate and to satisfy the customer so that he can be called for the next round of hiring. You are interested in finding a job that pays you well and develops your skills for your next job. The company's interest is in using you and your skills to make more than it costs them to recruit and pay you, perhaps to the point where they need to hire more people. And these interests can play against each other.

Some recruiters are terrible and just want to make money fast. In my experience, they come from large recruiting businesses that regularly churn and burn recruits. That hurts client companies and candidates. They'll cut salaries to get the internship, or take a large cut in salary as a fee, or hire an inappropriate candidate to get the job done quickly. However, some recruiters (especially 1 or 2 person boutique recruiters) want to build a strong brand so that they are more likely to work in the best interests of the client company and the candidate.

Some companies are terrible. They say they want to hire someone, but they often post jobs to signal their competitors that they are successful. Other companies want employees to join but have inappropriate performance expectations. If they get a candidate who doesn't immediately walk on the water who heals the sick and raises the dead, they will fire the candidate. This is where recruiters are valuable. To use a recruiter, a company must pay 20% of the applicant's salary as a fee. The only companies that use recruiters are those that are well capitalized. And when they spend that much money hiring you, they have a confirmation bias in your favor and you have more time to update yourself. Applying through a recruiter will limit your search to companies that are able and willing to pay a decent wage.