My iPhone 14 Pro Max battery is at 85% after a year. Why?

Can you tell me what is going on with battery on iphone 14 pro max this is really a shame after one year not max using my battery is 85% i cant belive it my xs max after 4,5 years max using was 93% how can you get better battery life and why dont you do something to stop and improve battery life

[Re-Titled by Moderator]