What I learned at college: physics, chemistry, optics, lots of heavy duty math - statistics, calculus, linear algebra, numeric computing, electrical engineering (analog and digital), how to write and publish, accounting, algorithms, a bit of management/business, and probably few other things I'm forgetting at the moment.
In my career I have done: computed cancer statistics for NIH, worked on a flight computer, done tons of avionics code, worked on a tank robot, computer vision, machine learning, and so on. Almost none of that would have been possible for me without at least a significant portion of the above skills. Chemistry comes in lowest, but it was still somewhat useful for the cancer stuff. And a tiny change in what jobs I had would have made the chemistry highly relevant (say, computational chemistry - tons of that going on around the beltway where I lived for a number of years). From here I can go most anywhere - finance quant jobs at 250K+, machine learning/big data, more computer vision, or what have you. You can .... write some more rails apps. If you are really good, sure, write the next rails, but I would say your options are far more limited than mine.
It's up to you and what you want to do, and what kind of potential you want to have available to you. University is not for learning a trade (by and large, medical school nonwithstanding); it's an opportunity to take in a lot of subjects at a depth you will never achieve on the job or part time (unless you have an ~170 IQ).
I'm sure people will post counterexamples to the above, and surely they exist; I argue simply that education == opportunity. If you have any kind of mind, 5 years of writing yet another rails app will start to bore you to tears. So, the question is, what will keep you from being bored? Inventing a new social app or such? Maybe school is less relevant. Taking on difficult intellectual challenges? It's pretty darn hard (not impossible, just very hard) to make your way without a strong math/science foundation. Also of note is how many people change their careers. Burn out in writing sw is pretty high. What skills will you have if in 5-10 years you want to be management, that CFO job starts to seem very interesting, and so on?
In short, I found my education exceptionally useful. You won't even be able to get an interview for many jobs, not because of snobbery (as is often claimed), but because there is no way you have the background to jump in and read original research in a new topic and deal with the math and algorithms in a sophisticated way. Only you can decide if that is of value to you or not.