Standing up from a seated position requires good strength of your proximal muscles, i.e. muscles close to your core, especially your glutes (butt muscles). If you don’t have good strength there you will need to use your arms to help push you up. Without thinking, many people have just settled into easy patterns and use their arms regardless, but this lets your proximal muscles get lazy and out of practice for when you do really need them.
TIP: Remind your glutes what they’re there for…. at least a few times per day, get up from your chair without using your arms.