Why do AI coding tools charge a subscription when users already have API keys?

I have been thinking about the pricing model of AI coding tools.

A lot of developers already have access to OpenAI, Anthropic, OpenRouter, Azure or local models, but still have to pay another monthly subscription just to use those models inside a coding agent.

I built CleanSlate around a different model:

Use your own API key and the product is free.

For people who do not want to manage keys, there is an optional $14/month managed plan.

I am curious what people here actually prefer:

Would you rather bring your own API key and control the cost, or pay a fixed monthly price for convenience?