Let me give you an example of where I live. I make (for here, not in general) reasonable money; most of my friends make considerably less than I do. I also happen to be lucky and live with room mates which drastically reduces my cost of living.

As it stands, if I wanted to rent my own apartment, 50% of my monthly income would be gone right there. That's not including utilities, internet, or food, and that's not a "nice" place - it's just what you can find. With those other expenses factored in, I'd be looking at roughly another 15% gone on top of that.

So as it is, just to keep a roof over my head, and keep myself fed and minimally entertained, it would cost 65% of my monthly income. I don't drive, but my transit pass is another almost 5%, so that brings it up to 70%; if I did drive it'd be another 10-15% on top of that for fuel and maintenance.

So somehow 30% of my income needs to be spread out for ALL of life (clothing, surprise bills, travel for visiting family, actually doing things you enjoy, etc.). On top of that, now there's saving for my retirement; you say 20-25% should go into savings. Being conservative and using the 20% figure, that leaves 10% of my monthly income to live off of. This also doesn't take into account any sort of savings for a mortgage or car, "Rainy-day Fund", or even allow for the remote possibility of ever traveling in your life.