Comment by atleastoptimal

If there were only one firm, then it would make sense to not sell inference. However OpenAI, Anthropic, Google are all in competition with each other to earn market share, developer goodwill, and to get reliable growth, selling inference is the best strategy, rather than making a thousand companies and needing to do the marketing, branding, differentiation, PR, etc for each one seperately.

Also, the AI companies learn a lot from selling their inference. They see what markets are growing fastest, what people are using AI for, information benefitted by the startups using their models putting way more effort into distribution than they are. With enough information, the model companies can then create a generic AI-enabled product (like they have over the past year) that factors in all the learnings the startups have undergone.