What's your opinion?

I have a friend who is always posting breastfeeding pics. She still lets her 4 yr old nurse, even when she doesn't have any milk. (She was pregnant and it dried up for a while, she called it "dry nursing." I am NOT JUDGING something I know nothing about, so spare the "*gasp* how dare you?!!!" comments. I am simply wanting to know the reason someone would do this? I mean, there are pics of her with the boob out, child holding the boob with her hand, nipple in mouth, giving the camera a thumbs up.....she's four. I don't understand. Help me understand this person lol. ETA...if there is a benefit to breast milk at 4 & 5 yrs old, why not pump?