What are the point of bond funds? (SWAGX)

I have about 25% bonds in my portfolio. I set this allocation back when I started, so I would at least Be somewhat protected. Looking at performance I might as well kept it in a HYSA or something. I know if interest rates drop bonds would go up but they are already fairly low and probably will be hikes in the future. Since 2017 this fund is down about 10%. At least the rest of my portfolio is in the SP500/total market. I’m not really asking for help just wondering why this even exists lol submit