If you're a small/FOSS project, it's not worth the time overhead to set up and maintain and troubleshoot.

If you're a large project, companies generally get more value paying for SaaS and letting devs do dev, rather than troubleshooting Jenkins for the billionth time.

The real value self-host brings is somewhere in the middle, where you need paid-level features with 0 fiat (and can pay in time instead).