In some cases they do. I work in a B2B vertical SaaS company and there’s both features that competitors build or rough edges around our features that make clients go „either we get X or we sign with someone else”. I agree though with the general sentiment that you don’t need SOTA models to build those - humans or humans + mid pack strong model will do.
It sounds that your business is selling completely agent-coded products. I don't know how long that will be viable, or even if it is right now.
In my part of the world, I am completely unable to sell completely agent-coded products, so even a SOTA model is useless. The majority of my time is spent on analysis outside of coding anyway, so when I bill it's not based on how many lines of code I've added, it's based on whether the goal of the customer is satisfied.
You can try, but where I am there's literally no point - anything I offer that I bill based on how long my agent will take will be counter-offered by an even cheaper person using the same agent.
I've been through this cycle a few times already. It's pointless.
I sell outcomes, not lines of code. When I can get paid for unlocking revenue or reducing costs, SOTA makes not one bit of difference.
In practice, this means that I now don't even engage with clients who lead with "we want this program written" or "we want this feature added to this code we own". Those types of clients, their expectation is that you'll never need to bill more than the time you used to meet with them and maybe an hour of "labour".
You can, of course, continue as normal, but the expectation from clients now is that code is, for practical purposes, free. I've had one client last year vibe-code a ping program using Claude Code just to "prove" to me that my custom board+design+code for their industrial flow controller could have been done by their AI subscription.
If your business is "selling code", you aren't gonna win. If your business is "selling solutions" then you don't need SOTA anyway.