Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why is mortgage interest deductible in the USA for a house you live in?
Taxes are a tool for achieving social policy goals. While Americans consider "Socialism" to be a curse, the US is in fact quite socialistic. Mostly towards corporations, but sometimes even the normal people, not only the "Corporation are people, my friend" (M. Romney) get some discounts. The tax deduction on mortgage interest comes as a tool to encourage Americans to own their homes. It is important, socially, for people to own their home to be independent, and in general contributes to the stability of the society. As anything, when taken to the extreme, it in fact achieves exactly the opposite, as we've seen in 2008, but when balanced - works well. Capital gain is taxed in the US, because it is income. Generally, any income is taxed. However, gain sourced from the sale of primary residence is excluded, up to a certain (quite large) amount from this tax (if lived in the residence long enough - 3 of the last 5 years prior to sale). This, again, to encourage Americans to upgrade their houses and make it easier for Americans to relocate when needed (sell one house and buy another without losing cash on taxes). As to "asset producing income" - that is true in the US as well. You cannot deduct your personal expenses, in general. Mortgage interest on primary residence is a notable exception, because it serves a social cause. Similarly, medical expenses are allowed as a deduction, if they're above certain limit, and many other things (for example - if a US person totals his car, and insurance doesn't cover the loss - it is tax deductible, above certain limit, the higher the income - the higher the limit). These are purely social policy breaks. Socialism, something Americans like to have, and love to hate. Many "anti-socialists" in the US are in fact taking advantage of these specific tax breaks the most, because for rich folks these are limited or non-existent (mortgage interest limited up to 1 million, medical expenses are allowed only above certain percentage of income, etc).