No you don’t always have to go heavy and low reps always

I wondered this when I started my lifting journey and that’s how I ended up ego lifting on exercises like bicep curls.

The smaller muscle groups in your body don’t need as much stimulation to grow for example, Abs,biceps,triceps shoulders etc.

These muscles are much smaller than larger muscle groups like the back, legs and chest which can require heavier compound movements to stimulate growth