I've not had a cell phone for over 10 years, except for a period of time when my job wanted me on call, so they paid for a blackberry... even then however I very rarely used it except a way to check my email without having to get out my laptop.
In any case, I haven't found it inconvenient hardly at all, except in the occasional situation such as a car breakdown. I do find it inconvenient when traveling however, but I usually only travel once or twice a year so I usually just load some minutes onto an old tracphone for those occasions
It is not really a money issue for me because I could probably afford to stay up to date with the latest and greatest gadget if I wanted to, but it is more of a philosophical issue for me. It seems phones today are designed to command as much of your attention as possible, and it seems that most of the phone usage that I observe is not a necessity. There's nothing wrong with that per se, but I do believe it makes it more difficult to live a balanced life. It is essentially the same reason that I don't watch or pay for television and movies.
These days, I'm not even sure it is less convenient to live the way I do... with all of the security & surveillance issues that have been cropping up, I am glad that I have inadvertently sidestepped a lot of the issues that are being revealed.