Suppose you bet the pass line, and a point is established on
the come out roll.
Can you now remove your pass line bet ?
No, you cannot change your mind and take back the pass line bet after a point is established.
If the point is 4 or 10, then your probability of winning
is only 3 / ( 3+6) = 1 / 3.
So, the casino will not want to give up its 2 / 3 probability
of winning your line bet.
If the point is 5 or 9, then the casino's probability
of winning is 1 - 4 / ( 4+6)
= 3 / 5.
So, the casino should refuse to let you take back
your bet.
If the point is 6 or 8, then the casino's probability
of winning is 1 - 5 / ( 5+6)
= 6 / 11.
So, again it is to the casino's advantage to not let you
take back your bet.