Personal Display Devices – Why do we even NEED Reading Glasses?

So, it occurs to me to wonder…

With so many people experiencing presbyopia as we age, why can't our personal reading devices (smart phones, tablets, computer monitors, kindles) adjust for that?

Just imagine the time saved and frustation averted seeking those misplaced reading glasses, especially for those of us who now enjoy perfect distance vision due to LASIK and modern cataract surgery!!

It seems to me that simple tweaks to these display devices could manage such a correction!