When you're younger, glasses don't have much, if any, effect at all. This is because your eyes can still perform the focussing act from the tip of your nose to whatever distance you're looking through your glasses.
However, as you age, presbyopia starts rearing it's ugly head. Even if you've never worn glasses at all, it'll gitcha. Around 40 or so, people start losing the ability to focus on objects close up.
This is the point where bifocals start entering your life, as you now need to correct your vision for close up as well as far away.
If you've entered this stage in your life, then talk to your eye doctor about it. Bifocals can be made to suit whatever need you have, including range time.
I wear progressive bifocals (you can't see the dividing line and they're "graduated" in strength depending on the angle I look through the lenses). Next visit I'm thinking about getting an extra pair of glasses to use at work for the computer.