My husband receives income in our residential state of SC. I receive income from NY (Remote Work). Why is NY taxing our entire joint income?

[Hal_Al]

Most likely, it only appears that NY is taxing all your income. Like many other states, NY calculates tax on all your income, then prorates the tax for the actual NY income. See lines 44-50 on form IT-203. 

[TomD8]

Do you physically perform any work within New York State - even for a single day?  If you do not, then your income is not subject to New York income tax.