There are soo many new lawyers for firms to choose from, why on Earth would a firm choose a non-aba graduate. Granted most never pass the bar so there are few to chose from but still why would anyone hire a non-aba student. (Insert here how the aba is bad yet your law school keeps trying to get approved).
If you pass the bar, there will be plenty of job available. I know that class rank, school, etc matter if you want to go corporate, but most people that go DL have different goals...
I will respond on the condition that you promise to learn how to use the quotes.

What if the DL student doesn't want to go work for a firm? GASP! Not everyone who goes to law school wants to work for a firm, you say?! Amazing! What if the DL student wants to start their own business, go into consulting, work in arbitration, mediation, financial enforcement in securities? My point was if you pass the bar, and you go to a DL school, you will have many opportunities. Also, I presume that many people who attend DL schools don't plan on going into Big Law. And before you ask, no I don't attend a DL school; I attend an ABA school on a full ride. I just support the idea that if you can pass the bar, then you have earned your right to practice law.
And just to respond to your question, of why a firm would choose a graduate from a non-ABA school over a graduate from an ABA school; what if the DL graduate has successfully litigated cases and won million dollar settlements. All the while, the ABA graduate misses a filing deadline and illustrates to his boss that his lack experience has made him a liability. Just one scenario I can imagine that would make the DL candidate very appealing to a firm.