Why is your Liberal Party conservative? Highly misleading.
There's actually two responses to this question. The first is to remember that outside the US, "liberal" basically means economically right wing (free markets and deregulation, etc). In the sense you mean, the Liberals haven't been liberal in either the social sense for a long time, and the Howard years pretty much entirely purged any small-l liberal influence from the party. There used to be a tradition of free votes on social issues but the fact that Tony Abbott enforced unanimous voting on the issue of gay marriage probably signified the party's final surrender to pure social conservatism.
The second and more interesting response is that the Liberals aren't even really consistently "liberal" in non-American terms either.
Historically the only thing unifying the political right in Australia has been opposing the Labor Party and organised labour. The Liberal Party wasn't even founded until 1949, before that there were an array of parties called things like Free Trade, Protectionist, Nationalist, United Australia, etc. The centre right has mostly existed in anti-Labor coalition since the 1920s.
Even today there's two right wing parties, the Liberal Party and the National Party.
Basically the Liberals historically represent the urban business interests, the Nationals are a rural/country party for graziers and farm owners. They exist in permanent coalition referred to as The Coalition. The details differ by state somewhat (in some states they're merged, in others the Nationals or a country party don't exist) but the division in the centre right is a feature of Australian politics.
Mostly at a federal level the differences are papered over and the coalition has been extremely displined to the point where we treat them as a single party.
It's usually had the amusing effect of meaning the Liberals have not only been fairly socially conservative for the most part, but also that they've not even been consistently small-l liberal in economic terms, due to the country interests' demands for protection and subsidies. It was actually Labor who drove the neoliberal agenda in this country in the 1980s and early 1990s.