It suits you to think that.

I bounce between the various extremes (yay bipolar) and from my actual experiences, I'm liked just the same whether I'm more reserved or more outgoing. Different people are likely to like me on one end or the other, but others like me most at the other end.

Most people like me no matter which end I'm at.

As for myself - I like the company of both outgoing and reserved people. Regardless of what end of my spectrum I'm at. Do you know what they all have in common though? They are friendly. They are kind. They are positive. They are accepting.

I go out of my way to introduce myself to the quiet people, as I know how it can feel to be shy. They aren't always shy though, just like I'm not always shy. Sometimes they approach me.

Your brother has people around him who like him because he puts himself out there. You don't. It's not because he is outgoing, although it can make it easier (not always though! A lot of the people I meet when I'm bouncy are people who are more likely to remain aquaintances).

You don't put yourself out there really. You seem to judge and blame (read your above post - you do both of those to your brother). You might not notice or intend it, but a lot of people probably do pick up on that vibe from you - a lot of people will back off once they pick up on the fact that the quiet person they've just started to talk to is actually rather bitter.