[josephjrobison]

What are some examples of those services that handle close to 100% of SaaS needs?

[abiogenesis]

Three examples: Authentication, payment processing, invoices:

https://thebootstrappedfounder.com/not-in-house-on-reinventi...

I would add things like sending newsletters (Mailchimp), monitoring (Sentry), various types of analytics (Segment, Hotjar) to the list.