Re: "So someone decided use different battery size for Model 3 "
Li cells can be large. Caravan owners use 100A cells to DIY their own battery packs. The use of small cylindrical cells is a throw back to when they were far cheaper per kWh and using them also means that when a bunch of them fail, the total capacity of the pack doesn't take a big hit all at once. Most other manufacturers besides Tesla use larger cells to save a lot of work putting packs together. Vehicle batteries come with pretty good warranties that run between 8 and 10 years so if there is an issue, chances are that you can get a new pack fitted for free.
The first Pre-Elon Tesla Roadster and the AC propulsion T-Zero used cylindrical cells since they were easy to get and they could be tucked away in any spare space.