Why does Europe use 50Hz?

Cost was the main reason Europe went with 220 volts (now 230). Counterintuitively, higher voltages allow the use of thinner wire, meaning less copper in the early days of power lines. Power companies could save money on wire by using 220 volts rather than 110.

No. It wasn’t the case also with the previous gen . Every HD game runs at 60 Hz. The emulated stuff usually runs at 50 Hz, e.g. PS1, PS2 Classics on PS3 and PS4, Original Xbox backward compatibility on 360, not sure about Xbox ONE.

50Hz corresponds to 3000 RPM . That range is a convenient, efficient speed for the steam turbine engines which power most generators and thus avoids a lot of extra gearing. 3000 RPM is also a fast, but doesn’t put too much mechanical stress on the rotating turbine nor AC generator.

The use of 50 versus 60 Hz is purely due to historical reasons, with companies in the US making 60 Hz equipment and those in Europe making 50Hz equipment so that they have a monopoly . This rivalry led to the split you see today.