Added protection against ISP and local snooping of traffic, either for commercial gain or by some local agencies in less-free countries where such things are common.

Bypassing geo restricted content is also a big one, says for people living abroad who want to enjoy access to content from their country of origin, or content that is not locally filtered.

Maintaining privacy when visiting websites that use your geolocation or IP to correlate your visits and profile you for advertisement based on your (more or less) precise location for instance.

Or maybe you want some added privacy when visiting some adult or political sites whose data may be breached or monitored and make your habits more public than you'd want.

In principle a VPN is just another level of privacy protection, as long as it's one that can be trusted, which is probably another issue since apparently not many can.