If you don't hit your growth milestones, the investor can take over your company. Venture investors tend to select one of two ownership control concepts. They either take a minority interest in the company that can increase if profitability targets aren't met, or they start with a controlling interest that declines as financial targets are met. Capital is risk-sharing. Equity capital measures how much the owners have risked in the company.
Equity is a cushion to absorb losses.
Debt capital must be repaid in good and bad times. The more debt a company has relative to equity, the riskier the loan. New companies are expected to have more capital. Not all dollars are equal to investors. You've spent dollars and sweat equity in product development, but if you can't get to market without investor money, your dollars are without value.