If everyone put the same mental effort into calf training as they do their arms then we’d see WAY more impressive calf development. That’s the biggest issue.

Aside from that, reps and frequency. People do too few reps, not enough volume (see my point above) and far too little frequency. If I had to grow my calves by two inches in six months in order to be paid a million bucks I’d train them 4-5x/week minimum. Same with my arms.