I'm me, and I'm calling her lazy. Because she is. The fact that it isn't "mandatory" for her doesn't make her any less lazy to not put in the same work as everyone else. Would you ever tell your boss, "I don't NEED to do this so I'm not doing it?" Because that's a great way to end up unemployed.
Irene just turned 33. She still promotes every comeback. Somehow I doubt 2 years is making much of a difference. Not to mention Taeyeon wasn't even promoting most of her early solo releases, which were like 5-6 years ago.