Same reason why the Fortune 200 company I'm currently doing some work for uses it. 70% discount on api costs compared with Anthropic, but access to the same Anthropic models.
Here every person gets $500 of copilot "credits" per month and that is a lot of use. $500 in Anthropic API gets used in 3 days.
The only disadvantage is that copilot cli has a very crappy and limited plugin system. For example a plugin can register a hook when a model calls a tool, but it's impossible to show a question to a user from such plugin.
Also it's "Autopilot" mode is designed to waste tokens. It injects things like "did you do absolutely everything you can about this? If not continue" and it's impossible to disable this without reverse engineering.
Here every person gets $500 of copilot "credits" per month and that is a lot of use. $500 in Anthropic API gets used in 3 days.
The only disadvantage is that copilot cli has a very crappy and limited plugin system. For example a plugin can register a hook when a model calls a tool, but it's impossible to show a question to a user from such plugin.
Also it's "Autopilot" mode is designed to waste tokens. It injects things like "did you do absolutely everything you can about this? If not continue" and it's impossible to disable this without reverse engineering.