A simple reason in for the increase of polls is its cheap availability and use of social media, both of these factors when interconnected can make it really easy for anyone with the right approach to create a poll. Those people who are in the policy making business also use the medium to get the latest of public opinions about certain issues which may help them create a relevant policy.
There is just one danger as I see it, that when it comes to politics the politicians focus more on getting votes by spreading and creating biased polls which help mold the public opinion to a certain extent.