The basic compound lifts alone (squats, deads, dips, chins, presses) are not enough to grow the arms and chest to their full potential. That's a problem, but the bigger problem is it's very easy to become elitist about being in the "compound exercise only" training club. It's natural to be proud of a great physique that was built on only two or four exercises. Two years ago I wouldn't be caught dead doing a curl or using a machine! But this mindset won't do you any good if you want to be big and jacked. To fill out lagging body parts, and specifically the arms and chest, we need more than what the compound exercises can offer.
What the compound lifts don't offer
They aren't offering us big arms and a big chest! Our arms and chest aren't puny because we aren't squatting enough. I don't want to hear about how the big compound lifts stimulate anabolic hormone release within the body, and by squatting more we create global growth across our body and that, in effect, will help even our arms grow. Bullshit. There are plenty performance enhancing drug using athletes out there who only do compound lifts, or mostly practice their sport who look like they have small arm disease. How about the Olympic lifters? Juiced to the gills, truck loads of food, compound exercises three times a day. Where's this "global growth" we keep hearing about in their arms and chest? Okay so their legs are frighteningly huge... because they train them! If hormone levels were all that mattered their arms would be freaky big too. Look, the reason their arms and our arms (and chests) are still small despite the fact we can all squat and deadlift over 2.5x our body weight isn't because we are still not squatting and deadlifting enough, or even pressing enough. And don't you dare google image me some buff olympic lifter. I don't care about exceptions.
Find me a guy at your local gym who only does olympic lifts and other compound movements who has 18 inch arms. You won't find him. Find me a jacked body builder who only does compound exercises. You won't find him unless he's scamming people on YouTube into believing that's all he does, scamming people who are already brainwashed into the "compound exercise only" club knowing that's exactly what they want to hear from him. You know what you will find at your local gym or a gym near you? A dude with normal/average blood androgen levels who sports around 18 inch arms flexed, under about 14% body fat who does tons of curls and tricep pushdowns. Yeah he's always done the compound lifts diligently, but he sculpted those arms with isolation work, and he spent years and years doing it. And he spent years and years eating well and eating lots of food. I've known many guys like this at many gyms. It's not uncommon.
So let's go to the doctor
Imagine tomorrow morning we both go to the doctor's office and we are both diagnosed with advanced stage "small arm disease" which will kill us this time next year unless we reverse it. The symptoms of small arm disease include: small arms. The parameter the doctor will use to gauge therapy efficacy is whether or not we can add an inch of biological muscle mass to our arms within the next month, otherwise the doctor will have to cut our arms off and put ketchup all over us. What exercises do you think the doctor will prescribe us for adding an inch to our arms? More squats and deadlifts? Hey, maybe pullups and dips right?
No. We're going to get a prescription for arm isolation exercises. We're going to go to the gym and do curls until our brains hemorrhage. We will do curls for heavy weight, curls for high reps. We will do drop sets, rest pause sets, cheat reps. We will do preacher curls, banded curls, the curl machine. We will do dumbell isolation curls, hammer curls, curls curls curls! And since the tricep is actually the biggest part of the arm, we will be working those in isolation too: skullcrushers. Close grip bench with boards. Overhead tricep extensions with dumbells and cables, and every single pressdown variation we can think of. We will isolate the crap out of our arms. Sarcoplasmic hypertrophy and Myofibullar hypertrophy, we won't give a crap which one it is, all that matters to us is getting bigger arms. We will do myofascial release work on our arms with a PVC pipe and hard ball for the first time in our lives to eliminate trigger points and expand the fascia to make more room for our muscles to grow. We'll be eating a lot more to give our arms the nutrients they need to grow. In short, growing bigger arms becomes a life or death situation. We need bigger arms fast!
However, growing bigger arms isn't a life or death situation. Whew! What a relief. So we won't need to change anything about the way we train! Let's continue doing dips and chins to grow our arms. Yep, they've sure been working really well. They sure have. Uh huh.... And let's continue believing that our arms will magically grow one day as a result of our squatting and deadlifting efforts.