Any political party is going to support the idea of "housing affordability". Who wouldn't!
The issue with housing affordability is that it relates to property prices.
Broadly speaking, the way to make housing more affordable is to reduce property prices.
Many voters are property owners. For most of these people, the bulk of their wealth is in property.
To make property housing more affordable, it's necessary to reduce the value of property, which in turn will reduce the wealth of a huge proportion of voters.
It doesn't help that major interest groups (such as banks) are also interested in property maintaining its value, considering it relies on the security of these properties.
For these reasons, most policies relating to housing affordability are symbolic and ineffectual.