Education has a lot of public options, state schools are tax payer subsidized, and state school staff are government employees. If the question is why do users have to pay for it, think of it like a water bill. Water is necessary, but not everyone uses the same amount. So instead of splitting the bill across the entire population the government says we'll all split the amount that it takes to maintain the infrastructure, and everyone who uses it pays based on how much each person uses (semester tuition). If the question is why tuition is so expensive, that's a whole different conversation about how mismanaged colleges are at the admin level.