The reason it is in the tax code is because the government is trying to provide economic incentive for a consumer behavior they deem beneficial (home ownership). When people own their homes, they are more likely to care about them and their neighborhoods, reducing negative outcomes of social interactions. Same thing, electric car tax rebates and solar installation tax credits. You can argue about whether or not those are good or bad things, but to do so, you'd probably have to go to
www.pilotspin.com because it will get political way too quickly.
When you give money for something, people are more likely to do it. When you charge them for something, they are less likely to do it.