yep. most fighters do go on when past their best, but it's all they've ever known so find it hard to leave alone. i know in some cases it's money based due to not handling it properly, but not all the time. when fighters leave at the right time like Calzaghe and Lewis for example, it really should be commended. as i can imagine it would be hard to just leave something that's basically been your entire life.
There's sadly more than a few. My favourites in theirs prime would be jones jr and Toney, well past the days of beating even B level competition :/