Why do some old people not greet the young people in the Masjid?

So I was at the masjid and I was waiting for the car with an elderly lady.
People stopped and said Salam to her and ignored me.
Keep in mind I was standing next to her.

Like they just ignored me. I think I even saw some of their smiles fade as they saw me...I THINK.

But yeah...it's not very nice. My mum said I should have said Salam to them when they ignored me but I felt like it might come of a little rude coz you know when you hold the door open for someone and they ignore you and you're like YOU'RE WELCOME! and it comes off as sassy? it might sound as if I'm being sassy to them.

Generally speaking the elderly need to stop hating on the youth and the youth should be respectful to the elders.