Because that is how MM make money. Offering liquidity with two-sided markets, selling what we deem high in value and buying what we deem low in value and hedge.
UPDATE AAPL at $208.00 I expect a 8%+ climb after earnings. $208 + 8% = 224 $224 - $215 (call strike) = $9 I will hold till after earnings.
@OptionsOptionsOptions knows what he is doing, he specializes in trading AAPL, GOOGL, AMZN.. options.
You only notice any pre-earnings trading pattern after the fact. Hindsight is always 20/20 - but it's no good for trading.