The company provided the following official statement.
"As part of that, we’ve decided to stop supporting 30-second unskippable ads as of 2018 and focus instead on formats that work well for both users and advertisers," said a Google spokesman.
Last year, YouTube introduced an unskippable 6-second ad format and it's believed that the company will push this unit more heavily going forward.
"YouTube realises that consumers don’t like unskippable ads," said Andrew Peake, managing director of integrated creative agency, VCCP. "At the end of the day, if you’re doing creative work that will engage right from the start, you haven’s got to worry too much."