If it is a crime not to file your taxes, how come we aren't taught how to file our taxes?

Good question. Because the education system is a joke

Everyone is presumed to know every law, even though it may be difficult or impossible to actually know ALL of the laws at any given moment.  An adult should take responsibility to find out when, where and how to file a tax return well before it actually needs to be done.  Many young people WANT to find out because they stupidly overpay their payroll taxes and want a refund.

When in doubt read the instructions.

Because you don't have to do it yourself. If you don't know how, and can't figure it out, then you can pay someone else to do it for you.

Because many people cannot do basic math. Use a good online program to step you through, or pay a preparer. P S You can teach yourself ... irs.gov.

you could always ask at a tax place to show you how to do it

You are.  In high school, the free education made available to all, everyone is taught that the forms are available at the post office and, nowadays, also on the Internet.  All of the forms come with a complete set of instructions that teach you how to fill out the forms.  

That being said, it's not the government's job to teach you how to not commit crimes.  It's a crime to not feed your child, but the government isn't responsible for teaching you how to feed your child.  It's a crime to have sex with someone who doesn't agree to have sex with you, but the government isn't responsible for teaching you how to get someone to agree to have sex with you.

they actually, in fact have classes specifically to teach you that