1) I suspect that the primary motive to trade is to facilitate the fantasy that exists about trading, that with a moderate amount of effort, you can make a disproportionately large amount of money.
2) This 'get rich quick' attitude is in a large part fuelled by the value system that we live in which is shaped by our fallibilities. In order to have any success, you need to overcome such problems as:
a) Changing your relationship with money
b) Letting go of the need to be right
c) Fear of success
d) Fear of failure
e) Validation of self through wealth
f) Looking for meaning in life through increased spending power
As most people will not be prepared to confront even one of these examples, never mind their own personal and exhaustive catalogue of predispositions that will ultimately lead to failure, they realise the pursuit is too difficult and then fail or give in.
Ultimately the drop-out rate is so high because people are not prepared to make the investment to become good. People will always go for the easy option.