Eh? Big players still run AGPL licensed services. The concern is not about the access to source code.

The concern is livelihood. When a big player swoops in, they can completely decimate your business because of shear scale advantages, they can undercut you into bankruptcy. And while sharing the source under even GPL is noble, it's just also kneecapping your ability to make and grow a new business if it's a tool/service that has market traction. The OG author having access to that modified source code does absolutely nothing to help them.

The big players are literally seagulls waiting to steal your current and future customers.

> The concern is not about the access to source code.

That is a big part of the concern, yes. That anyone can copy your work, setup a competitor, and never give anything back. Copyleft licenses, and the AGPL in particular, ensure that those changes are made public, which benefits everyone, including the original project.

> When a big player swoops in, they can completely decimate your business because of shear scale advantages, they can undercut you into bankruptcy.

That's not a guarantee. In fact, many businesses built around copyleft licensed products can thrive, in ways that their competitors cannot. The original authors understand the code base, the product, and their users much better. They have first-mover advantage on any new features, and have full control over the project's direction. They can use these advantages to build a business that is difficult to compete with, even for much larger and more powerful competitors.

In the open source world, the value of a company hinges on the quality of its product and the community around it, not on market hype, speculative valuations, and venture capital. It is more difficult to build unicorns and make investors rich with this approach, but focusing on the user avoids many of the wrong incentives that make most companies user hostile. Many companies fail because the leadership doesn't understand this, nor the philosophy behind open source, and they simply want to use it as a marketing tactic.