Brand new drugs tend to take a while to get on insurance formularies. I believe Mounjaro is still missing in most formularies. Lilly wants people on their drug, not the competition.
This is not only an American issue. I've seen people in the UK struggle to get access to treatments and devices through the NHS. Canada tends to follow what the US is doing even though they have their more socialized system. It all tends to be a bit of a mess with brand new drugs and devices. And Mounjaro is new as of last year (approval less than a year ago?).
No, drug approval takes time everywhere with a health care system. Heck I've been on methylphenidate for my ADHD for almost 15 years now, and it's still off-label when prescribed to an adult in the UK according to the NICE.