It may or may not be true that nobody does it, but non-residents of IN are required to file an IN tax return if they have any Indiana-source income.
https://www.in.gov/dor/individual-income-taxes/filing-my-taxes/who-should-file-a-tax-return/
Indiana-source income includes "salaries, wages, fees, commissions, and all other types of income received by a nonresident employee for services performed in Indiana."
https://www.in.gov/dor/files/reference/ib39.pdf
Therefore the income you derived from services or work you provided in Indiana, is by law taxable by Indiana.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
