How low is your social iq?
The bright light quite literally represents a joke where the fans of Usopp and Sanji get blinded by their heroism/awsomeness. That's the joke and that's why the light/glowing is there.
They don't start glowing out of nowhere for no reason like Zoro just to attract their toddler fanbase to the screen. Unless you have an explanation on why Zoro creates auras filled with every RGB light color.
btw I'm still waiting for all those times Sanji and "other characters" were glowing just as much as Zoro. I legit can't remember that prior Wano