It gives you more specialization in more advance cases that most primary care doctors don't normally encounter. Sometimes that extra challenge, enrichment, confidence gives it some personal value of worth. It won't necessarily translate into monetary value of worth.
Some jobs require residency as a pre-requisite. Is it necessary in order to get a good job? Well, it makes you more desirable as an applicant. Everything is about desirability it seems for humans. Imagine doing a residency makes you more desirable by training you and giving you an atheletic, toned, sexy body. And the better jobs out there are sexy potential mates that you want to match with. While it is not an impossibility, and sometimes it relies on luck, competition based on geography, or other factors, if you want a sexy potential mate to notice you or extend an invitation, you better be pretty competitive and desirable yourself.
Sometimes you are the settle-er and they are the reach-er. Sometims you are the reach-er and they are the settle-er. Sometimes you are the perfect match for each other despite how desirable any of you are. But when push comes to shove, the more desirable you are, the more chance you have landing a hot babe.
And let's say you don't necessarily land that super job/babe (as what happens in life) that pays a ton more, at least you got training that gave you a hot, confident "body" that you can flaunt and be content with.