I've noticed that too. I kept my personal smartphone for years until I needed to replace it and the replacement phone was noticeably bigger when I first put it in the pouch I use to hold my phone.
When I ported my former office number to a mobile phone, the phone they shipped me was even bigger than my personal smartphone is and the former barely fits in my front pocket. If phones get any bigger, it will be more difficult for them to be as mobile as they once were.
I totally get that mobile phones have pretty much morphed into personal digital devices that do more than send/receive calls. However, they will become too cumbersome if they get much bigger (think of the original cell phones that came with their own carry pouches and antennae because they were so large/bulky for use in one's car).