No one likes ads, especially if they are done in Flash technology. Not enough that they are annoying, but Flash ads are also inefficient and consume a lot of computing power. Therefore HTML5 is much better and multi platform (and multi device) technology. Everyone depends on the fact that advertising reached the widest possible audience, so Google decided to not support Flash ads.
Of course, such big company as Google can not implement so drastic changes from day to day. Therefore they published an information, that Flash ads will be supported for a year. The first restriction will be implemented already this year. Namely, starting from June 30th, 2016 it will not possible to upload ads built in Flash into AdWords and DoubleClick Digital Marketing. A half year later, i.e. starting from January 2nd, 2017 Flash ads will not be longer run on the Google Display Network and through DoubleClick. The purpose of these actions is to force all advertisers to move on HTML5 format.
Currently, Google does not plan to block video ads which use Flash. However, it seems clear that also it will happen in the near future. A lot of people think that Flash technology will disappear from the Internet in two years.