However, some activities work best with bifocals situated elsewhere.
Since bifocal lenses often cost a bit more than single vision ones, bifocals that stick onto regular lenses are a good alternative for those who can't afford to spring for the pricier pair of lenses.
For example, you wouldn't want to choose a very shallow frame if you need to fit in bifocals.
No one knows whether you have single vision lenses or bifocals.
Your eyes will never get accustomed to bifocals if you switch from type to type.