Create a proper seated mode for better accesibility
Why it's important to implement it? People have different heights, physical limitations should not translate into the virtual world.
Result Everybody can look at each other at the same height
More info on the image below :)

┆Issue is synchronized with this Jira Task
Playing "Devil's Advocate" here: What if you want to be at a different height/size? Could be an option as well. Or possibly, the avatar model could be at a different scale than the others.
My opinion, I'm partially agreeing with you: The default should be the same height, but, make it configurable.
Kind of the VR chat avatars, that they all have different heights themselves
As discussed on avatar discord channel recently I actually have a use-case where I do purposely want avatars to be at different heights. In Human Factors/Ergonomics teaching I want to use VR to encourage my Engineering/Design students to empathise with people who might be in a wheelchair or particularly tall who then experience different designs in my virtual world and struggle with issues of reach, vision and clearance. So although I think in everyday use there are equality-based arguments for same height avatars being default, it's also important to make it easy to create different height ones in Hubs.