Vesting of shares does not necessarily imply that you give anyone the right to fire you. For example, a company with several founders might choose to use vesting even if they never take or need VC funding, to deal with the case where a founder voluntarily chooses to leave early on. And while an arrangement with a VC could potentially grant them the ability to fire a founder, it doesn't necessarily have to, and I've seen plenty of cases where the founders did not agree to such terms (especially in cases of VCs signing on with well-established companies).