I don't see many reasons why a 54 year old single guy wouldn't want to be with a young 24 year old girl. The 20 year olds are more attractive than women their age and it's a status symbol (not many men that age can pull it off). However the age gap will be enormous and will be felt very quickly by both parties. The older guy will quickly notice the lack of experience, sophistication and understanding of subtleties in life that only come with time. The younger girl will be turned off by the less outgoing nature of the older guy and less interest in sociability and interest and things which are modern.
Ofcourse it could work (Look at Michael Douglas and Catherine Zeta-Jones) but longevity of such a relationship will probably not be very stable.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~