I really like characters who are older, I feel the same in that they just don't get enough exposure. But you're right in that it's just not common.
We write comics with characters that are older than us, for the most part, but still sometimes around the same range that you mentioned.
The two main characters in Mal de Ojo are around 35 - 36
In Love Labs, they are around 35 and 38
An old comic I was working on had main characters ranging from 11 to 65 and 70 (The older characters have a lot of backstory and aren't just there to grow the story of the younger characters hah)