[gansbrest]

Pretty much what cialowicz said.

At the end of the day someone needs to answer a simple question - "Is the product functional right now / after the last release?".

If you don't have QA team you either rely on your product person to "give it a spin" or your engineering who are generally not very excited about clicking through the product multiple times (more often than not, they'll just leave it at the unit test phase and move on).

In small orgs that product person could be your CEO or CTO, meaning this will give them an easy false-escape into "micro-management" mode (aka feeling productive by doing low priority tasks) vs forcing them to make strategic decisions or worse, they'll just block the entire pipeline.

QA creates a natural quality gate looking at the product from the user's perspective, putting pressure at the engineering to deliver quality work and gathering leadership feedback at critical points only.