Bloomberg says drugmaker Amgen signed up 20,000 Copilot seats. Thirteen months later, Amgen employees are using OpenAI's ChatGPT. Amgen expanded its use of ChatGPT earlier this year after seeing the technology improve and hearing from employees that it helped with such tasks as research and summarising scientific documents.

Senior Vice President Sean Bruich said: "OpenAI has done a tremendous job making their product fun to use. Copilot is still a "pretty important tool, but more so for use with Microsoft products such as Outlook or Teams."

The same pattern is playing out across other firms who expected Copilot to slot in smoothly.

Even though Copilot runs on OpenAI's models and offers similar features like summarising, drafting emails, analysing data and image generation, it lacks the momentum. ChatGPT had already won hearts and keyboards at home and that familiarity is proving hard to beat.

As of June 2025, ChatGPT pulls in 800 million weekly active users, with three million paying business customers. Copilot has stalled at 20 million weekly users for the past year despite contracts with Volkswagen, Accenture and Barclays worth tens of millions and covering more than 100,000 licences each.

Microsoft banked on its old formula of dominating the OS, wedge the new product into Office and wait for IT departments to do the rest. But this time, the end users had already made their choice.

To make matters worse, Microsoft is having to swing the axe again, cutting between 6,000 and 7,000 jobs which is nearly three per cent of its workforce. That comes on top of the 10,000 it culled two years ago.

Turns out familiarity, not forced integration, really wins the AI arms race.