I thought a friend of mine was on steroids for many years, but he has been 5'11 and 205 for at least the past four years. If he was on something, he would have gained.
Look, you have to do steroids to understand how they work in the long run. There are competitors who have juiced for decades and never moved up a weight class. If your first cycle was 200mg of Deca and 100mg of Winstrol weekly and you keep doing that same dosage range you wont keep making major gains cycle after cycle. The ceiling of gains is reached pretty rapidly, even with drugs. Just look at Jocelyn Pelletier and Kenny Jones both of whom have cycled for a long time.
When "your friend" gained 20lbs during that month of d-bol it was mostly just water retention, since you say he didn't eat more food so there was nothing to build actual contractile tissue from (I'm talking about energy from calories, not just protein). Not even steroids let you build muscle out of thin air.