delta not calculated from actual stk and option price than why would so many people use delta to determine how many contracts to hedge? isn't p n l is from actual stk and options price? why use theory delta which is not from really directly related to stk and option price?
Delta tells you the change in option price if the stock price changes by $1. There is no time frame attached to it.
Yes, delta is used to determine the hedge ratio, but since factors other than the stock price affect the option price, you also need to take into account other greeks. Delta hedging is not a set and forget method, you need to constantly rebalance the hedge to remain delta neutral.
delta is a lagging value that is delta of 0.25 today does not implied tomorrow option price would decrease 0.25 should the stk price decrease one dollar?