It has already been mentioned, but the airline pilot needing a degree is a lot like a military officer needing a degree. Both jobs can be well and easily done by qualified folks without a degree, but it demonstrates that the person who stuck it out and got a four year degree has the communication skills, aptitude, and drive and perseverance to complete a long term course of instruction. It took me 9 years to get my degree. No, I am not a doctor. There were a lot of bad decisions, mistakes, and skipped classes along the way. Finally, I got a taste of what life is like in the real world without it (turns out most quality employers care) and I did what it took to finish and get a good gpa. It was a long journey, but I am a better person, and I dare say more professional pilot, because of it.
I am not downing anyone's decision to not get one. Sometimes life gets in the way, sometimes it just isn't your thing. That's fine, it almost wasn't mine. Just know that without it in this profession, you are at a distinct disadvantage.