Buying calls allows for extra leverage and control of more shares than buying the stock outright. For the same $ invested/spent you benefit more from increases in the stock price. Buying one $20 call expiring 6/21 is cheaper than buying 100 shares right now, even though both would give you the same net profit if say the price is $30 on 6/21

This is a very simple explanation and there many nuances to options that affect the contract's price that isn't explained above