Typically it's so crowded that it's impossible to find who you're meeting. So, I don't understand why people typically meet there other than tradition
It's not a tradition. People meet there because it's a spot everyone knows, right outside the station, with a ton of signs telling you where it is. If not Hachiko people usually say "let's meet at the green train" which is another thing right next to the Hachiko statue and has no history about loyalty attached to it whatsoever.