2L vs 3L in job searches

 I found that there are a lot of law firms that only search for 2L's rather than 3L's soon to graduate and take the bar. While I am sure there are a multitude of factors, I think the prime reasons boil down to just two or three.

One reason, giving the benefit of the doubt, is that the firm cannot afford to expand and take on another licensed attorney right now. However, I have seen this practice more prominent on the bigger firms that can definitely afford taking on a couple more attorneys and not have it financially harm the firm. 

However, the bigger reason I have seen and came to the conclusion is that the firms, even ones with 20+ attorney's, don't need to bring another licensed attorney for more money on, when if they get enough 2L labor, they can pay at a much cheaper cost the work needed to be done and then only review it and make simple adjustments. So they can take on much more work at a lower cost. 

I personally saw this as a firm of 17, was looking for a niche experience/background of their applicants but said the prospects of finding those that had it were extremely low. So when I had the exact experience and background into the field that they were hoping for, they kept repeating the 2L search parameters. They said they were looking for people with this background/experience so that they did not have to spend a lot of time training in the niche terms and character of the businesses they would be representing and understanding the facts of the cases that they encounter. But they only wanted to bring on 2L's. So my summation was that they just wanted the cheaper labor to bring on temporarily and the background/experience was to lessen how much time they have to train the 2L temps. 

Has anyone else witnessed?