Investment doesn't always implicit into money but also efforts. Doing bounty is not an easy task if you work on such multiple bounties. If you do it full-time then it is considered as a job(?) already since most of your time is only on doing task such as advertising ICOs on social media and the bitcointalk forum itself. Investments doesn't also mean that they are already investors, it is a different word.
You are right. Our time and our hard work to complete tasks and rules are one of investment. That's a substitute for money because we will also get a token at the end of the campaign.