Today it is already widely accepted that out of school education exceeds formal education in content and knowledge and that it is not a plus, but a necessity. However, unlike formal education, educators working in informal settings are often volunteers or/and they do those activities on top of their daily jobs. The research questions we pose here are (i) what motivates people to volunteer in K-12 Science, Technology, Engineering, Mathematics and Computer Science (STEM-C) informal education, (ii) what could help to motivate people who are currently demotivated, and finally (iii) what we can do not only to attract new volunteers, but also to retain the current ones. We collected and analyzed opinions of faculty staff, students and volunteers involved in K-12 STEM-C outreach activities conducted at University of Zagreb Faculty of Electrical Engineering and Computing, Croatia where five years ago, we started our outreach program named SUZA - From school to science and the academic community. The results of our research study show a wide span of reasons why (and why not) people volunteer in our activities, together with their general attitudes toward K-12 STEM-C outreach activities. Although the results are mostly in line with research in the field, there are some specifics which could relate to specifics of volunteering in K-12 STEM-C fields and could benefit wider community.