The problem is you assume you will hold untill expiry. A lot of things can happen between when you initiate the position and expiration.
Look at it this way. If fair value for a particular option is 1.00 and the spread is 0.95/1.05, you buy at 1.05 and sell at 0.95. Let's say your winning ratio is 50/50. You win 2 or lose 2. In the long run you win 0.95 but lose 1.05 any way you cut it with 50% success. It makes no difference if you buy or sell the option.
How this applies to real trading is that you may win 95% of the time selling options, but the 5% that you lose wipes out the 95% winning profits you made. In the end you're still a net loser. Flip for buying options.
The only way to consistently win without an edge is to be a MM and buy/sell below/above fair value. Bookies don't lose (often).
Look at it this way. If fair value for a particular option is 1.00 and the spread is 0.95/1.05, you buy at 1.05 and sell at 0.95. Let's say your winning ratio is 50/50. You win 2 or lose 2. In the long run you win 0.95 but lose 1.05 any way you cut it with 50% success. It makes no difference if you buy or sell the option.
How this applies to real trading is that you may win 95% of the time selling options, but the 5% that you lose wipes out the 95% winning profits you made. In the end you're still a net loser. Flip for buying options.
The only way to consistently win without an edge is to be a MM and buy/sell below/above fair value. Bookies don't lose (often).