A lot of companies do recruit older guys, however, there are a lot of ex-mil with 2/3000 hrs behind them out there. This way the airline gets a blend of youth and experience.
These guys also suffer from ageism with the regionals. I think the earlier point about wanting young malleable FO's is valid. I also agree with Scroggs' comment about wanting experience commensurate with age. Individual airlines will decide what level they require.
As the Big Boys open up their recruitment, there will inevitably be vacancies at the other end. Things can only get better!