The warranty is 2 years. Warranty is the confidence a company has that it will last as long as that. Batteries eventually die, so that is the one part in mobile devices we can guarantee needs to be replaced.
Manufacturers make bigger devices difficult to repair - so it being a small form factor is just an excuse. When they try and it fails then is the time to consider if it’s feasible. Fairphone products are probably average at best but you can at least replace the batteries in a small device like their earbuds (Fairbuds), and assume they will get better at making their repairable devices.
I would say the warranty is probably confidence that a percentage will last that long, and the amount they have to replace is cheaper than the business they lose not offering it.
edit: and no argument that companies are also working to make devices less repairable, i’m cynical that more often then not they are trying to design devices that last exactly as long as the warranty.
