I bet most of the people actually don't the whitepaper, sometimes I don't too. They might just put "best ICO to invest in 2018"  keyword on google and invest on it.
But I agree with @whirlcoin, if you really want your investment to be worth it then read the whitepaper, it doesn't guarantee the project would be successful if you read it though. But at least you'll be at ease because you put your hard-earned money in a project you learned already. But I believe 'luck' play a part too in here.