It's Hayati
Week Nine: Greeting Others
Abu Hurairah (RA) narrated that the Prophet (ﷺ) said, "The young should greet the old, the passerby should greet the sitting one, and the small group of persons should greet the large group of persons."
- Source: Sahih Bukhari
The Prophet (peace and blessings be upon him) is telling us the importance of greeting others in certain scenarios.
If you are young and you see people who are older than you, it is your job to greet them first. If you are passing by a fellow Muslim brother or sister and they are sitting down, it is your job to greet them first. Whether they're older or younger than you. And if you are entering a room, for example, a masjid, you need to be the first one to greet those that are already in the masjid.

Not only is this Sunnah, but it is respectful to greet our brothers and sisters in Islam when we see them or when we are passing by them.
Let this be a reminder for us all, including me, to always remember to greet our Muslim brothers and sisters.