If they are THAT into enacting legislation based on "surveys", what if a majority wanted free ponies and applesauce for everyone, would they simply say:"The people have spoken, lets make it law!"?
First of all, this isn't really a survey in the normal sense. Australia's constitution specifically requires referendums in certain circumstances, and connected with that, national plebiscites have been used on a few occasions in our history (and only a few) to address specific questions. Prior to the 2013 election, the Liberal/Nation coalition promised that Australia would only move towards same sex marriage if a plebiscite was held on the specific issue. That promise was repeated prior to the 2016 election.
Unfortunately, the Labor opposition aided by the Greens decided to use their numbers in the Senate to try and block such a plebiscite from happening, instead arguing that same sex marriage should become law without any sort of public vote on the issue. The government found a way around that blockage by having a postal vote conducted by the Australian Bureau of Statistics for which new legislation was not required. Labor and the Greens then tried to stop this from happening in the High Court and failed.
In other words, the very fact that this vote happened at all was only because the conservative side of politics insisted the Prime Minister keep a promise twice made to the Australian people that would get a vote specifically on this issue, in the face of concerted opposition by the left to stop that from happening. Once the left failed in their repeated efforts to block the vote, that's when they started saying "Oh, it's just a survey. Not a real vote." This article has for some reason decided to use their term - basically legitimising the dishonesty and anti-democratic tendencies of the left.
This was a national vote of 100% of the Australian electorate, with procedures in place to ensure that everybody who chose to vote would have that chance, and to ensure that nobody would be able to successfully vote more than once. It wasn't some sort of random survey of a small group. And nearly 80% of people who were eligible to vote did so - considerably more than the US gets for most Presidential elections (most elections in Australia are compulsory so we can't make a comparison like that here).
As to why we have to follow the procedure of introducing a Bill to Parliament after the national vote, that is down to the Australian constitution which is derived (mostly) from principles in the British constitution. One of these is the concept of Parliament Sovereignty - and it's also the reason why the Brexit Referendum in the UK is having to be followed by legislation in Parliament. There's no constitutional mechanism that allows such a national vote as this to automatically take effect - it has to be done by legislation introduced after the vote is taken. That's how our constitution works.