Indeterminate tomato plants grow continuously throughout the season, producing endless vines and foliage but surprisingly little fruit unless you prune them. Left unpruned, these plants waste energy on excess growth instead of directing it toward fruit production.
Removing the right parts forces the plant to channel energy into larger, faster-ripening tomatoes that actually taste good. Pruning also improves air circulation around the plant, preventing fungal diseases that thrive in dense foliage, and makes spotting pests significantly easier.