1) It Cuts You Off From The World
Being on your phone all the time cuts you off from reality and your surroundings. You end up so engrossed in what you're doing that you don't notice what's happening around you.
2) The World Feels Cut Off From You
If you're on your phone, people may be reluctant to talk to you or interrupt what you're doing which can cause missed opportunities to meet someone new or for your friend to talk to you about things. If you look busy, then nobody will want to bother you.
3) It Gets Addicting And Stressful
It's hard to get out of the habit of constantly being on Instagram, Tinder, and other social media apps and one you're using them they become a part of your personality. And trying to constantly keep up with everything online and trying to keep your online persona looking a certain way can be stressful.
4) It's Money That Can Be Spent Elsewhere
The cost of buying and maintaining a plan on your phone can be expensive. I'd personally rather spend that money on something I need than on a phone.
5) You Learn To Be Dependent On It
It can become something that you feel unsafe leaving the house without or like you wouldn't know what to do if you lost it. Sometimes you can end up putting too much trust on the idea of having one that you don't learn how to navigate the world without it (mostly for teenagers on this one).
So here are a few reasons why I don't personally carry a phone on me, but everyone is different and I don't expect everyone to agree with not having one. Just my own lifestyle.
Thank you for reading!