I graduated over twelve years ago from a US college with debts amounting to about 30,000. My financial situation was so precarious when I left college that I was crashing with friends here and there, and had no fixed address. Consequently, the loan people could not find me, and for my part, it felt like there was no point getting in touch because whatever they'd ask me to pay, I wouldn't be able to, so I chose the head-in-the-sand approach.
Eventually, over time, I moved abroad, and things picked up, and now, finally I'm in a reasonable financial position.