For impact play specifically? Well this is of course gonna differ for everyone but there's a TON of amazing energy exchange that I get from giving pain that is desired. I probably don't need to say it but controlled pain makes our body do some really weird things and activates a wild chemical cocktail for many people, so being able to give someone that 'pain high' is incredibly fun for me, as well as seeing and teasing out their reactions. I also just really like it for its own sake! Bruises and welts are beautiful aesthetically, and just the feeling of landing blows on someone is definitely a huge adrenaline spike. If I'm in a dungeon or other semi-public place like that, it's also a huge voyeuristic rush, of people watching me give pain and imagine themselves in the situation of the recipient or just enjoying it artistically, especially because I tend to make my own playlists and hit my play bottoms rhythmically (yes, EVEN MY KINK is a rhythm game, lollll!)