Yeah we are. But phones are more powerful, with bigger screens and power hungry electronics. Plus consumers want smaller, lighter phones, so with the higher density they make the batteries smaller. It's a balance.
Thats exactly why I was disappointed that all the top of the line phones went with 1440p or 4k displays. I have a 27" monitor that is 1440p, I don't need that kind of resolution on my Note 5. I wish it was still 1080p display and better battery life.