Why get good grades if you have valuable skills?

I used to think that way (and kind of still do). In my opinion it depends on several things. If you want to go to college, yes, get good grades. If you can make a good living freelancing or as a web developer without an "education", good grades may not be necessary. Take some time to think it over, because if you change your mind a decade from now, it will be much harder to get a degree.

I will point out, though, that grades traditionally speak something about a student's character, and people may or may not take that the wrong way. For example, some web development internships (if you're interested in those) look at your GPA. I'm not sure how much a company values your grades, but students who get good grades are generally hard-working, responsible, and meet deadlines - values that I'm sure companies want. For a freelancer, it would probably be a different issue.

Another thing to consider depends on what you want to do in the future. For example, I'm interested in the education sector, not just building tools but actually developing an educational framework from ground-up based on technology. (There are a lot of things wrong with our current edu system - assuming you're in the USA. One problem is what you mentioned - learning things that aren't really valuable.) If I want people to listen, it would certainly help if I had a MA or PhD. It shows people, "Hey, I've been there, done that, and I know it isn't the best way."

Like someone once said:
If you don't like the rules
Follow the rules
Get to the top
And change the rules

I mean, good grades are probably the result of you being a good student. I'm not against education at all (I do think though that the current education system sucks, but those are different cases to discuss).

The more you learn the better (even if the knowledge itself is useless it might stimulate your mind positively).

My point is, as long as you don't need to sacrifice your skills or a bigger vision for your grades, you should still get them IMHO. Why not have valuable skills AND good grades?

Getting good grades doesn't matter and the education system is inevitably going to deliver a mediocre experience, even at the university level. University is good for two things imo: the piece of paper so you can get your first job, and also simply for the experience of growing. Uni is a great place to find yourself, it should be a time of introspection and exploration. But you need good grades to go to a good uni.

From my perspective, school and higher education is not about making money.
I dropped out of high school and found immediately a job as a web developer (January 2000) because that was my hobby and I had the skills. I kept on learning and progressed through various stages, became even a CTO and made more money than most University professors ever dared to dream about.

3 years ago, I decided I wanted to go to college. Got my GED, finished community college with an AA in Japanese and Liberal Arts, and got accepted into every university I applied to (incl. UCLA and USC). I settled for the University that gave me a full-ride scholarship and finished my bachelors last December while continuing to work full-time. I just finished my first semester of my master's degree at USC (also on a scholarship) for a field that will never make me more money than I could earn in software engineering.

So why did I do it?
Human growth.

For me, college is NOT about making money or securing a job. Is it beneficial? Sure is. Some opportunities you will not have without an advanced degree. Some opportunities will close because you have an advanced degree.

My perfect GPA does not help me secure any job. But it is an indicator how much work I am capable of producing and I know how much I can handle.

So what do you think? Do good grades matter to you?