I hit a 5-wood and 7-wood longer and straighter than I do a 4-iron and/or a 5-iron or 6-iron? Why is that?

I am a middle-aged golfer - about 5'7''. Have never used custom clubs. Have never been able to hit long or mid-irons. Can hit 7-iron, 8-iron, 9-iron, PW. Have 6 and 5 iron in the bag, but rarely use then.