Because this guy is always there, singing to travellers.
As people arrive to drop off their checked bags, he assists customers with the process and sings to them. It's one of a dozen different tunes that he sings, of course, midway through any song he'll insert instructions on where people need to go next or a simple "have a nice day" at an appropriate time in the melody.
He always elicits a smile out of me, even when I'm stressed and worried about not making my flight (which that security checkout line can easily inspire). He doesn't have to do what he does. His job is to take the bags and perhaps answer questions from confused travelers - but he adds that little extra touch, offering something unique to the day of each person who sees and hears him.
It's a small thing that he does, but it puts smiles on peoples faces.
Last time I went through Pearson, I joked with one of the agents who was inspecting my hands for residue (drug residue? gun oil residue? bomb chemical residue? driver's booger residue?) by asking her if he ever comes in to work in a grumpy mood. She laughed and smiled and said not that she'd ever seen.
I don't know the man's name, but I admire him and appreciate that little thing he brings in people's lives every day. He also inspires me to consider what little things I might be able to do to make another person's day that much brighter.