I recently did a marathon stream and had my mods running !kraffles all throughout the marathon. One thing I noticed was that if they ran the raffle and I didn't say anything, X number of people would enter. If they ran the raffle and I announced it or made everyone aware who were maybe watching in full screen or not paying as much attention to chat, then the number of people who entered would grow to be quite the factor of x.
Since interaction is always key, a sound effect or notification on screen would be an amazing way to get people interacting when these types of events are going on.