People on such short trips usually don’t stick around long enough to realize how ineffective they are being.  In Uganda, I got used to seeing groups of young people come for week-long visits at the orphanage where taught English. They would play with the kids, give them a bracelet or something, and then leave all-smiles, thinking they just saved Africa. I was surprised when the day after the first group left, exactly zero of the kids were wearing the bracelet they had received the day prior. The voluntourists  left thinking they gave the kids something they didn’t have before (and with bragging rights for life). But the kids didn’t care, because what they really wanted was school uniforms, their school fees to be paid, guaranteed meals, basic healthcare, and the like — the basics.
 
Worse, they can even be harmful to children who struggle with abandonment issues.  This should not be understated; have you ever considered the negative impact it routinely has on kids after they bond with someone for a week, and then that person disappears from their life? If your justification for going on these trips is “seeing the smiles on the kids’ faces”, then you’re part of the problem.