The EU mandated microUSB charging ports on phones, thus reducing the "cable clutter" that existed 5-odd years ago.
Now, the EU is mandading the other end of the charging cable, the actual, physical charger is plugs into. Meaning, you'll only need a single charger, with a USB port in it, to charge your flip phone, your 4" mini-smartphone, your 6" phablet, and your 10" tablet.
Right now, each device has it's own charger, with it's own specs (how many volts at how many amps). And you generally can't charge a tablet using an older phone charger.
So you end up with a handful of different chargers in your drawer that you have to pick through to charge each device, or you end up with a drawer full of chargers you never use as you just plug everything into the most power charger you have (generally the one for the tablet).
Standardising on a single charger would eliminate all the extra chargers gathering dust in people's junk drawers.