I think we all know that while 5% of lifters get it, 95% don't. For these guys gaining muscle is seen as some sort of complex puzzle. We can head to any forum on the net or local gym and see scores of guys lifting who aren't making progress. I believe it is reasonable to say that there are 3 reasons they fail:
1) They aren't persistent.
2) They aren't training hard enough on the right lifts, and aren't focused on progression in some form or fashion.
3) They aren't eating properly.
Regarding the eating...9 times out of 10 when I see someone training hard but not gaining muscle they simply aren't eating enough. They are generally:
A) Basing calorie intake off a random BMR calculation.
B) Eating "healthy" which is generally a lower fat diet devoid of enough sustenance to add any weight.
I see a lot of guys I really want to help eating too clean and too tight. They are 2-3-4-5-6-7-10 years in and have yet to achieve gains that are what we would call quality beginner gains.
These are the folks I preach to when I say "eat big". Eat big doesn't mean eat like a pig...but there has to be a happy medium. If someone bumps their calorie intake by 500 per day it's simply not going to turn them into a sumo wrestler in a year. Considering they haven't made any substantial gains at all, adding 500 daily calories will in all likelihood lead to a very minimal fat gain.
It takes a lot of aberrant/excessive eating to gain weight to the point where you weigh 240-270 pounds. I know because I've been on this ride from time to time. When I exited the military I had extra money for the first time in my life and was able to eat for pleasure.
From 1994 to 1997 I gained 50 pounds of fat, and during those 3 years my eating was uncontrolled and excessive. I had a lot of Mountain Dew along with a diet of fast food, chips and sweets.
In the 14 years since I haven't gained a pound. Well, scratch that...I started lifting again and regained about 20 pounds of muscle (or so) while maintaining my weight, so I did a fairly quality re-comp ...or whatever it is you guys call losing fat and building muscle.
The question that is at the root of this discussion is
If you're training hard and adding weight to the bar but not gaining muscle year in and year out, what's broken?
If you've been training for 5 years and haven't even begun to touch beginner gains, what's broken?
My picture below was taken 18 months after returning to the iron after a long layoff. I did a 100 day cut, then a slow bulk for the next 15 months or so.
Now I understand that not many guys want to weigh 270 pounds, but apply this method to someone who started at 140-160 pounds. I believe once they hit 180 to 190 they will have an amazing amount of muscle mass; probably all they will ever want or need.
Look at Graeme McKillop. He added 42 pounds in 3 years. When doing his recomp after an injury, he ate 5500 calories per day.
Muscle memory and 5500 calories a day got my up to my biggest point ever at 205 pounds at about 13% body fat.